What's that alarm code?
Type what's on the unit's display. You get what it means in plain words and, for the common ones, what a reefer tech looks at first. It's free, with no sign-up.
These are a technician's first checks, not a service manual. The same number can mean different things on different controllers, so confirm it on the unit and in its manual. Refrigerant and high-voltage work is for qualified technicians. Thermo King and Carrier have not reviewed or approved this list.
Nothing for “” in these lists.
Check the display and try again, with the letters as they show. Still nothing? Email the code and the unit's model and a reefer tech will tell you what it means.
Thermo King
Thermo King reuses numbers across its controllers. Where a number has more than one meaning, the one most controllers use comes first.
-
0
No Alarm
Other controllers use 0 for: Supply Air Sensor Open Circuit.
-
1
Reference Channel Fault
Other controllers use 1 for: Supply Air Sensor Short Circuit.
-
2
Evaporator Coil Sensor
Other controllers use 2 for: Ambient Air Sensor, Evaporator Coil Average Sensor and Return Air Sensor Open Circuit.
What to look at first
If it is Evaporator Coil Sensor:
- Faulty evaporator coil temperature sensor
- Coil sensor harness open/short or wet connector
- Sensor reading inconsistent with box conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
3
Return Air Sensor
Other controllers use 3 for: Control Return Air Sensor, Discharge Air Sensor and Return Air Sensor Short Circuit.
What to look at first
If it is Control Return Air Sensor:
- Faulty return-air temperature sensor
- Return-air sensor harness or connector issue
- Sensor misplaced / poor airflow over the probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
4
Discharge Air Sensor
Other controllers use 4 for: Control Discharge Air Sensor, KVQ Sensor and Evaporator Coil Sensor Open Circuit.
What to look at first
If it is Control Discharge Air Sensor:
- Faulty discharge-air temperature sensor
- Discharge sensor harness open/short
- Sensor seeing recirculation or blocked supply
Common mistake: Controller replacement before the sensor and harness are proven.
-
5
Ambient Air Sensor
Other controllers use 5 for: Spare 1 Channel, Evaporator Coil Sensor and Evaporator Coil Sensor Short Circuit.
What to look at first
If it is Ambient Air Sensor:
- Open/short or high-resistance ambient sensor
- Damaged ambient sensor harness or connector
- Sensor reading out of expected ambient range
Common mistake: Controller replacement before the sensor and harness are proven.
-
6
Water Temperature Sensor
Other controllers use 6 for: Spare 2 Channel, Humidity Sensor and Compressor Current Too High.
What to look at first
If it is Water Temperature Sensor:
- Faulty coolant temperature sensor
- Sensor harness open/short
- Actual cooling-system issue reflecting on the sensor
Common mistake: Controller replacement before the sensor and harness are proven.
-
7
RPM Sensor
Other controllers use 7 for: Spare 3 Channel, Return Air Sensor and Compressor Current Too Low.
What to look at first
If it is RPM Sensor:
- RPM sensor failed or air-gapped incorrectly
- RPM sensor harness open/short
- Actual engine speed problem (prove sensor first)
Common mistake: Controller replacement before the sensor and harness are proven.
-
8
Field Voltage Channel
Other controllers use 8 for: Remote Return Air Sensor.
-
9
High Evaporator Temperature
-
10
High Discharge Pressure
Other controllers use 10 for: High Discharge Pressure or Temperature, ECOP Pressure Warning and Heater Current Too High.
What to look at first
If it is High Discharge Pressure:
Unit protecting the compressor.
- Blocked or dirty condenser coil / poor airflow
- Condenser fan not running or low airflow
- Overcharge or non-condensables (prove with gauges after airflow is clean)
Common mistake: Bad HP transducer before you’ve proven condenser airflow and fan.
-
11
Unit Controlling on Alternate Sensor
Other controllers use 11 for: Unit Controlling on Discharge Air, Temperature Out of Range, Unit Controlling on Remote Return Air and Heater Current Too Low.
What to look at first
If it is Unit Controlling on Alternate Sensor:
- Primary control sensor failed, unit on backup
- Primary sensor harness fault
- Control logic selecting alternate after out-of-range
Common mistake: Controller replacement before the sensor and harness are proven.
-
12
Sensor Shutdown
Other controllers use 12 for: Temperature Out of Range Above and Evaporator Fan High Speed Current Too High.
What to look at first
If it is Sensor Shutdown:
- Critical sensor failure forcing protective shutdown
- Multiple sensor channels failed
- Harness damage affecting control sensors
Common mistake: Controller replacement before the sensor and harness are proven.
-
13
Check Sensor Calibration
Other controllers use 13 for: Temperature Out of Range Below and Evaporator Fan High Speed Current Too Low.
What to look at first
If it is Check Sensor Calibration:
- Sensors need calibration / grade setup
- Reference drift between probes
- Recent sensor replacement not calibrated
Common mistake: Controller replacement before the sensor and harness are proven.
-
14
Defrost Terminated by Time
Other controllers use 14 for: Evaporator Fan Low Speed Current Too High.
What to look at first
If it is Defrost Terminated by Time:
- Defrost ran to time limit without terminating on temp
- Defrost termination sensor issue
- Heavy icing or heater underperformance
Common mistake: Heater bank replacement before termination sensor and airflow/icing are checked.
-
15
Glow Plug Check
Other controllers use 15 for: ADC Calibration Failure and Evaporator Fan Low Speed Current Too Low.
What to look at first
If it is Glow Plug Check:
- Glow plug open or high resistance
- Glow relay/driver circuit fault
- Low battery voltage under preheat
Common mistake: Glow plugs before battery voltage under preheat is measured.
-
16
Digital Input Failure
Other controllers use 16 for: E2PROM Fault, Arrays Do Not Match, Manual Start Not Completed and Condenser Fan Current Too High.
-
17
Engine Failed To Crank
Other controllers use 17 for: E2PROM Fault, Storage Has Failed and Condenser Fan Current Too Low.
What to look at first
If it is Engine Failed To Crank:
- Low battery / poor cranking voltage
- Starter or starter-relay circuit fault
- Safety interlock preventing crank
Common mistake: Starter replacement before cranking voltage and fuel delivery are proven.
-
18
High Engine Water Temperature
Other controllers use 18 for: Power Supply Phase Error.
What to look at first
If it is High Engine Water Temperature:
Cool-down before you dig deeper.
- Low coolant level or air in the cooling system
- Blocked radiator / poor radiator airflow
- Failed water pump or stuck thermostat
Common mistake: Bad coolant temp sensor before you’ve checked level, radiator face, and belt-driven pump.
-
19
Low Engine Oil Pressure
Other controllers use 19 for: Temperature Too Far From Setpoint.
What to look at first
If it is Low Engine Oil Pressure:
Do not run it.
- Low oil level or external leak
- Oil pressure sensor / switch fault
- Worn oil pump or clogged oil filter (less common, prove level and sensor first)
Common mistake: Oil pump failure before dipstick level and sensor circuit are proven.
-
20
Engine Failed to Start
Other controllers use 20 for: Auto Start, No Start Shutdown and Defrost Time Too Long.
What to look at first
If it is Engine Failed to Start:
Prove power and fuel before parts.
- Low battery / poor cranking voltage
- Fuel supply issue (no fuel, air in system, lift pump)
- Preheat / glow plug fault on cold starts
Common mistake: Bad starter or ECU before battery voltage under crank and fuel delivery are proven.
-
21
Cooling Cycle Check
Other controllers use 21 for: Undercool Warning and General Cooling Fault.
-
22
Heating Cycle Check
Other controllers use 22 for: Underheat Warning, General Heating Fault and Capacity Test 1 Error.
What to look at first
If it is Heating Cycle Check:
Unit isn’t making expected heat.
- Heating mode not actually engaged (mode/valve/solenoid)
- Hot-gas or heat circuit fault (valve, coil, wiring)
- Sensor or control logic seeing underheat vs setpoint
Common mistake: Alternator or charging fault, this code is the heating cycle check.
-
23
Cooling Cycle Fault
Other controllers use 23 for: Undercool Shut Down, Cool Timeout and Capacity Test 2 Error.
-
24
Heating Cycle Fault
Other controllers use 24 for: Underheat Shut Down and Heat Timeout.
-
25
Alternator Check
Other controllers use 25 for: Alternator/Battery Charger Check, Charging System Failure and Return and Discharge Air Sensor.
What to look at first
If it is Alternator Check:
- Alternator not charging or belt slip
- Regulator / field circuit fault
- High resistance at battery terminals
Common mistake: New alternator before belts, terminals, and resting voltage are proven.
-
26
Refrigerant Capacity Check
Other controllers use 26 for: Pretrip Coil Failure and Vapor Injection Error.
What to look at first
If it is Refrigerant Capacity Check:
Unit isn’t pulling like it should.
- Low refrigerant charge / leak
- Restricted TXV / filter-drier / liquid line
- Compressor wear or weak valves (prove pressures and temps first)
Common mistake: Compressor replacement before charge, airflow, and expansion device are proven.
-
27
Pretrip Return Air
Other controllers use 27 for: Motor RPM Failure.
-
28
Pretrip Abort
Other controllers use 28 for: Pretrip Discharge Air.
What to look at first
If it is Pretrip Abort:
- Pretrip step failed a check
- Sensor or actuator out of range during pretrip
- Operator aborted or precondition not met
Common mistake: Skipping the failed pretrip step detail and shotgunning parts.
-
29
Damper Circuit
Other controllers use 29 for: Pretrip Damper.
What to look at first
If it is Damper Circuit:
- Damper actuator stuck or seized
- Damper solenoid/coil open
- Damper position feedback fault
Common mistake: New damper assembly before coil power and free movement are proven.
-
30
Damper Stuck Closed
Other controllers use 30 for: Damper Solenoid.
What to look at first
If it is Damper Stuck Closed:
- Damper actuator stuck or seized
- Damper solenoid/coil open
- Damper position feedback fault
Common mistake: New damper assembly before coil power and free movement are proven.
-
31
Oil Pressure Switch
Other controllers use 31 for: Pilot Solenoid Failure, Oil Pressure Sensor and Low Pressure Cut Out.
What to look at first
If it is Oil Pressure Switch:
Prove the circuit before you condemn the engine.
- Oil pressure sensor or switch open/short / out of range
- Connector corrosion or harness fault
- Actual low oil pressure (only after sensor circuit and oil level are proven)
Common mistake: High compressor temperature or a bad compressor, this code is the oil pressure sensor or switch.
-
32
Refrigeration Capacity Low
Other controllers use 32 for: Condenser Coil Temperature Sensor Open Circuit.
-
33
Check Engine RPM
Other controllers use 33 for: Throttle Solenoid and Condenser Coil Temperature Sensor Short Circuit.
-
34
Modulation Circuit
Other controllers use 34 for: Modulation Valve and Ambient Air Temperature Sensor Open Circuit.
What to look at first
If it is Modulation Circuit:
- Modulation valve coil open or stuck
- Valve harness/connector fault
- Controller not commanding modulation correctly
Common mistake: New valve before coil resistance and harness are proven.
-
35
Run Relay Circuit
Other controllers use 35 for: Bypass Valve and Ambient Air Temperature Sensor Short Circuit.
-
36
Electric Motor Failed to Run
Other controllers use 36 for: Electric Motor Overload.
What to look at first
If it is Electric Motor Failed to Run:
- Standby motor overload / thermal trip
- Phase loss or wrong voltage
- Contactor or motor winding fault
Common mistake: Motor rewind before phase rotation and supply voltage are proven.
-
37
Check Engine Coolant Level
Other controllers use 37 for: Low Refrigerant Level.
What to look at first
If it is Check Engine Coolant Level:
- Low coolant level
- Coolant level sensor/switch fault
- External leak at radiator/hoses/pump
Common mistake: Bad coolant sensor before level, radiator face, and pump are proven.
-
38
Electric Phase Reversed
Other controllers use 38 for: Real Time Clock Battery and Check Lithium Battery.
What to look at first
If it is Electric Phase Reversed:
- Incoming phase rotation incorrect
- Phase-sensing circuit fault
- Site power wiring error
Common mistake: Motor rewind before phase rotation and supply voltage are proven.
-
39
Water Valve Circuit
Other controllers use 39 for: E2PROM Checksum Trip.
-
40
High Speed Circuit
Other controllers use 40 for: Pump Down Time Out.
-
41
Engine Coolant Temp Check
Other controllers use 41 for: Pretrip Failure and Pulp Sensor Failure.
What to look at first
If it is Engine Coolant Temp Check:
- Faulty coolant temperature sensor
- Sensor harness open/short
- Actual cooling-system issue reflecting on the sensor
Common mistake: Bad coolant sensor before level, radiator face, and pump are proven.
-
42
Unit Forced To Low Speed
Other controllers use 42 for: Program Failure and Customer Configuration.
-
43
Unit Forced To Low Speed Modulation
Other controllers use 43 for: Power Frequency Low and Return Air Temperature Too High.
What to look at first
If it is Unit Forced To Low Speed Modulation:
- Protective logic forcing low speed
- Related high-temp/pressure or config limit
- Throttle/high-speed circuit problem
Common mistake: New valve before coil resistance and harness are proven.
-
44
Fuel System Check
Other controllers use 44 for: Three Phase Current Imbalance and Return Air Temperature Too Low.
What to look at first
If it is Fuel System Check:
- Low fuel level
- Fuel level sender fault
- Fuel delivery restriction (filter/air)
Common mistake: Fuel pump failure before level, filters, and sender are proven.
-
45
Hot Gas Circuit
Other controllers use 45 for: Power Frequency High.
-
46
Air Flow Check
Other controllers use 46 for: USDA 1 Sensor.
What to look at first
If it is Air Flow Check:
- Restricted evaporator airflow / icing
- Evaporator fan not running at commanded speed
- Blocked return or discharge path
Common mistake: Charge top-up before evaporator airflow and fan are proven.
-
47
USDA 2 Sensor
Other controllers use 47 for: Remote Sensor.
What to look at first
If it is Remote Sensor:
- Remote sensor failed or disconnected
- Remote harness damage
- Connector corrosion at remote probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
48
Check Belts/Clutch
Other controllers use 48 for: USDA 3 Sensor.
-
49
Spare Sensor 1
Other controllers use 49 for: Spare 4 Sensor.
What to look at first
If it is Spare 4 Sensor:
- Spare channel sensor fault or unused channel noise
- Harness short on spare input
- Configuration expecting a spare sensor
Common mistake: Controller replacement before the sensor and harness are proven.
-
50
Reset Clock
Other controllers use 50 for: Compressor Off Current and Compressor Current Out of Range.
What to look at first
If it is Reset Clock:
- Clock not initialized or lost time
- Backup battery failed
- Controller clock circuit fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
51
Compressor Cooling Current
Other controllers use 51 for: Compressor Over Load and Power Line Voltage Too Low.
What to look at first
If it is Compressor Over Load:
- Compressor current outside expected band
- Compressor mechanical load / seizure beginning
- Current-sense circuit out of calibration
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
52
Heat Circuit
Other controllers use 52 for: Compressor Mod Cool Current, Modulation Valve Circuit and Probe Error.
-
53
Economizer Valve Circuit
Other controllers use 53 for: Heating Capacity, Heater Current Out of Range and High Pressure Switch Off Error.
-
54
Test Mode Timeout
Other controllers use 54 for: Defrost Capacity, Defrost Current Out of Range and High Pressure Switch On Error.
What to look at first
If it is Defrost Current Out of Range:
- Defrost heater current out of range
- Heater element or contactor fault
- Current-sense calibration issue
Common mistake: Heater bank replacement before termination sensor and airflow/icing are checked.
-
55
Check Engine Speeds
Other controllers use 55 for: Evaporator Fan High Speed.
-
56
Evaporator Fan Low Speed
Other controllers use 56 for: Compressor Temperature Too High.
What to look at first
If it is Evaporator Fan Low Speed:
- Evaporator fan motor or inverter fault
- Fan not achieving commanded speed
- Fan harness or power supply issue
Common mistake: New fan motor before command voltage/amps and free spin are proven.
-
57
Evaporator Fan High Speed
Other controllers use 57 for: Fan Rotation, Condenser Fan Current Out of Range, Evaporator Fan Invertor and FAE Device Error.
What to look at first
If it is Condenser Fan Current Out of Range:
- Condenser fan motor/current fault
- Fan rotation/sensing wrong
- Fan contactor or inverter issue
Common mistake: New fan motor before command voltage/amps and free spin are proven.
-
58
First Config Block
Other controllers use 58 for: Sensor Calibration Check, Phase Sensor Error and Condenser Fan Roadside.
What to look at first
If it is Sensor Calibration Check:
- Sensors need calibration / grade setup
- Reference drift between probes
- Recent sensor replacement not calibrated
Common mistake: Controller replacement before the sensor and harness are proven.
-
59
Second Config Block
Other controllers use 59 for: A+ Datalogger Full, Compressor/Condensor Fan Invertor, Delta Current Error and Condenser Fan Curbside.
What to look at first
If it is A+ Datalogger Full:
- Datalogger memory full or write error
- Download overdue
- Datalog hardware/EEPROM fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
60
Generic Datalogger Full
Other controllers use 60 for: Humidity Sensor Error.
What to look at first
If it is Generic Datalogger Full:
- Datalogger memory full or write error
- Download overdue
- Datalog hardware/EEPROM fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
61
Low Battery Volts
Other controllers use 61 for: Real Time Clock Invalid.
What to look at first
If it is Real Time Clock Invalid:
- Clock not initialized or lost time
- Backup battery failed
- Controller clock circuit fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
62
Ammeter Out of Calibration Range
-
63
Engine Stopped - Reason Unknown
Other controllers use 63 for: Hot Gas Circuit Failure and Motor Rotation Failure.
-
64
Pretrip Reminder
Other controllers use 64 for: Pretrip Precondition.
-
65
Abnormal Temp. Differential
Other controllers use 65 for: Datalogging Error and CO2 Too High.
What to look at first
If it is Datalogging Error:
- Datalogger memory full or write error
- Download overdue
- Datalog hardware/EEPROM fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
66
Low Engine Oil Level
Other controllers use 66 for: CO2 Too Low.
What to look at first
If it is Low Engine Oil Level:
Top up and find why it’s down.
- Oil consumption or burn
- External oil leak
- Oil level sensor fault (false low)
Common mistake: Sensor fault before the dipstick agrees with the alarm.
-
67
Liquid Line Solenoid Circuit
-
68
Internal Fault Code
Other controllers use 68 for: Gas Analyzer Error.
-
69
Dehumidity Valve Circuit Failure
Other controllers use 69 for: Gas Analyzer Calibration Error.
-
70
Hourmeters Exceed 499999
Other controllers use 70 for: Hourmeters Exceed 99999 and O2 Sensor Error.
What to look at first
If it is Hourmeters Exceed 499999:
- Service hourmeter limit reached
- Hourmeter counter fault
- Reminder due, not necessarily a hard fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
71
Hourmeter 4 Exceeds Set Limit
Other controllers use 71 for: Hourmeter 1 Limit Exceeded and CO2 Sensor Error.
What to look at first
If it is Hourmeter 1 Limit Exceeded:
- Service hourmeter limit reached
- Hourmeter counter fault
- Reminder due, not necessarily a hard fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
72
Hourmeter 5 Exceeds Set Limit
Other controllers use 72 for: Hourmeter 2 Limit Exceeded.
What to look at first
If it is Hourmeter 2 Limit Exceeded:
- Service hourmeter limit reached
- Hourmeter counter fault
- Reminder due, not necessarily a hard fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
73
Hourmeter 6 Exceeds Set Limit
Other controllers use 73 for: Hourmeter 3 Limit Exceeded.
What to look at first
If it is Hourmeter 3 Limit Exceeded:
- Service hourmeter limit reached
- Hourmeter counter fault
- Reminder due, not necessarily a hard fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
74
uP Reverted to Default Settings
Other controllers use 74 for: Hourmeter 4 Limit Exceeded.
What to look at first
If it is Hourmeter 4 Limit Exceeded:
- Service hourmeter limit reached
- Hourmeter counter fault
- Reminder due, not necessarily a hard fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
75
uP RAM
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
76
uP EPROM
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
77
uP Failure
Other controllers use 77 for: uP EPROM Checksum.
-
78
Data Log EPROM
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
79
Data Log Overflow
-
80
Compressor Temp Sensor
What to look at first
- High compressor head temperature (airflow/charge)
- Head-temp sensor fault
- Condenser fan or charge problem
Common mistake: Controller replacement before the sensor and harness are proven.
-
81
High Compressor Temp
Other controllers use 81 for: Copeland Sensor and Compressor 1 Head Temperature.
What to look at first
If it is High Compressor Temp:
- High compressor head temperature (airflow/charge)
- Head-temp sensor fault
- Condenser fan or charge problem
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
82
High Compressor Temp Shutdown
Other controllers use 82 for: High Compressor 1 Head Temperature.
What to look at first
If it is High Compressor 1 Head Temperature:
- High compressor head temperature (airflow/charge)
- Head-temp sensor fault
- Condenser fan or charge problem
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
83
Compressor 2 Head Temperature
Other controllers use 83 for: Low Engine Coolant Temp.
-
84
Restart Null
Other controllers use 84 for: High Compressor 2 Head Temperature.
What to look at first
If it is High Compressor 2 Head Temperature:
- High compressor head temperature (airflow/charge)
- Head-temp sensor fault
- Condenser fan or charge problem
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
85
Forced Unit Operation
Other controllers use 85 for: Compressor 1 Circuit.
-
86
Failed Discharge Pressure Transducer
Other controllers use 86 for: Compressor 2 Circuit and ECOP Sensor Failure.
What to look at first
If it is Failed Discharge Pressure Transducer:
- Discharge pressure transducer failed
- Transducer harness open/short
- Actual high-side pressure event
Common mistake: Transducer replacement before gauges confirm actual pressure.
-
87
Suction Pressure Sensor
What to look at first
- Suction pressure sensor failed
- Sensor harness open/short
- Actual low-side pressure anomaly
Common mistake: Controller replacement before the sensor and harness are proven.
-
88
Controller Failure
Other controllers use 88 for: Modulation/KVQ Valve.
-
89
Electronic Throttle Valve Test
What to look at first
- ETV stepper/valve failed or stuck
- ETV harness/connector fault
- Controller ETV drive issue
Common mistake: New valve before coil resistance and harness are proven.
-
90
Electric Overload
-
91
Electric Ready Input
-
92
Sensor Grades Not Set
Other controllers use 92 for: Condenser Sensor.
What to look at first
If it is Sensor Grades Not Set:
- Sensors need calibration / grade setup
- Reference drift between probes
- Recent sensor replacement not calibrated
Common mistake: Controller replacement before the sensor and harness are proven.
-
93
Low Compressor Suction Pressure
Other controllers use 93 for: Motor Control Module.
What to look at first
If it is Low Compressor Suction Pressure:
- Low suction pressure, charge/restriction/TXV
- Suction transducer reading low
- Evaporator airflow or load issue
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
94
Unloader #1
Other controllers use 94 for: Air Exchange Motor.
-
95
Unloader #2
Other controllers use 95 for: Transfresh Star 1.
-
96
Low Fuel Level Alarm
Other controllers use 96 for: Transfresh Star 2 and Low CO2 Level.
What to look at first
If it is Low Fuel Level Alarm:
- Low fuel level
- Fuel level sender fault
- Fuel delivery restriction (filter/air)
Common mistake: Fuel pump failure before level, filters, and sender are proven.
-
97
Output Module Lost Communications
Other controllers use 97 for: Remote Return Air Sensor Failure and Compressor Temperature Sensor Open Circuit.
-
98
Fuel Level Out of Range Alarm
Other controllers use 98 for: Compressor Temperature Sensor Short Circuit.
-
99
High Compressor Pressure Ratio
What to look at first
- High compressor head temperature (airflow/charge)
- Head-temp sensor fault
- Condenser fan or charge problem
Common mistake: Compressor replacement before airflow, charge, and the related sensor are proven.
-
100
Heater Fan Failure
-
101
Unit Controlling on ECOT Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
102
Evap Coil Outlet Sensor Too Cold
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
103
Low Fuel Level (propane)
What to look at first
- Low fuel level
- Fuel level sender fault
- Fuel delivery restriction (filter/air)
Common mistake: Fuel pump failure before level, filters, and sender are proven.
-
105
Receiver Tank Pressure Solenoid Circuit
What to look at first
- The solenoid coil open or stuck
- Solenoid harness/connector fault
- Controller output to that solenoid failed
Common mistake: New valve before coil resistance and harness are proven.
-
106
Purge Valve Circuit
-
107
Condenser Inlet Solenoid Circuit
-
108
Door Open Timeout
What to look at first
- Door left open beyond timeout
- Door switch stuck or misadjusted
- Door-switch wiring fault
Common mistake: Cargo claim before door switch and actual door events are proven.
-
109
Discharge Pressure Sensor
Other controllers use 109 for: High Discharge Pressure or Sensor.
What to look at first
If it is Discharge Pressure Sensor:
- Discharge pressure transducer failed
- Transducer harness open/short
- Actual high-side pressure event
Common mistake: Controller replacement before the sensor and harness are proven.
-
110
Suction Line Solenoid Circuit
-
111
Unit Not Configured Correctly
What to look at first
- Controller configuration incomplete or corrupt
- Wrong model/options programmed
- Config write interrupted
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
112
Remote Evaporator Fan
What to look at first
- Evaporator fan motor or inverter fault
- Fan not achieving commanded speed
- Fan harness or power supply issue
Common mistake: New fan motor before command voltage/amps and free spin are proven.
-
113
Electric Heat Circuit
-
114
Multiple Alarms
-
115
HPCO Switch Failure
-
116
HPCI Switch Failure
-
117
Auto Switch from Diesel to Electric
-
118
Auto Switch from Electric to Diesel
-
119
Digital Valve Error
-
120
Alternator Exciter Circuit
Other controllers use 120 for: Suction Pressure Sensor Error.
What to look at first
If it is Alternator Exciter Circuit:
- Alternator not charging or belt slip
- Regulator / field circuit fault
- High resistance at battery terminals
Common mistake: New alternator before belts, terminals, and resting voltage are proven.
-
121
Liquid Injection Circuit
Other controllers use 121 for: Discharge Pressure Sensor Error.
-
122
Diesel/Electric Relay Circuit
Other controllers use 122 for: O2 Sensor Calibration Error.
-
123
ECIT Sensor Failure
Other controllers use 123 for: Data logger Battery Error.
What to look at first
If it is ECIT Sensor Failure:
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
124
ECOT Sensor Failure
Other controllers use 124 for: Cold Treatment Restart.
What to look at first
If it is ECOT Sensor Failure:
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
125
CO2 Sensor Failure
What to look at first
- CA/TransFRESH sensor or star channel fault
- CA harness/connector issue
- Actual atmosphere out of band
Common mistake: Controller replacement before the sensor and harness are proven.
-
127
Setpoint Not Entered
Other controllers use 127 for: Alarm General Unit Error.
-
128
Engine Run-Time Maintenance Reminder #1
Other controllers use 128 for: Supply Air Temperature Probe Error.
-
129
Engine Run-Time Maintenance Reminder #2
Other controllers use 129 for: Return Air Temperature Probe Error.
-
130
Electric Run-Time Maintenance Reminder #1
Other controllers use 130 for: Evaporator Coil Temperature Probe Error.
-
131
Electric Run-Time Maintenance Reminder #2
Other controllers use 131 for: Ambient Condenser Temperature Probe Error.
-
132
Total Unit Maintenance Reminder #1
Other controllers use 132 for: Power Module Sensor Error.
-
133
Total Unit Maintenance Reminder #2
Other controllers use 133 for: Power module Network Error.
-
134
Controller Power On Hours
Other controllers use 134 for: Controller Error.
-
135
Check Spare Digital Input
Other controllers use 135 for: Power Module Error.
-
136
Check Spare Digital Output
Other controllers use 136 for: Transducer Circuit Error.
-
137
Damper Gear Motor Heater Failure
Other controllers use 137 for: Sensor System Overload.
-
138
DAS Real Time Clock Battery
Other controllers use 138 for: AVL Sensor Error.
What to look at first
If it is DAS Real Time Clock Battery:
- Clock backup battery depleted
- Battery holder/contact issue
- Controller clock circuit fault
Common mistake: Controller replacement before the battery and its contacts are proven.
-
139
Internal File Handling Error
-
140
Evaporator Section Too Hot
-
141
Autoswitch Diesel to Electric Not Allowed
Other controllers use 141 for: PM Heat Exchanger Too Hot.
-
143
Check Drain Hose Circuit
-
144
Loss of CAN Communication
-
145
Loss of Controller ON Feedback Signal
-
146
Software Version Mismatch
-
147
Fan Speed Output Faulted
-
148
Autoswitch Electric to Diesel Not Allowed
-
150
Alarm Sensor Under Range
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
151
Alarm Sensor Over Range
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
152
Alarm Sensor Invalid
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
153
Failed Expansion Module Flash Load
-
154
Low Suction Pressure Switch Failure
-
156
Suction/Liquid Heat Exchanger Bypass Valve
-
157
Profile Mismatch
Other controllers use 157 for: Data Logger Battery Failure.
-
158
Primary Software Failed to Load
-
159
SMART Alarm: Battery Life
-
161
DAS Real Time Clock Invalid
What to look at first
- Clock not initialized or lost time
- Backup battery failed
- Controller clock circuit fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
162
SMART Alarm: Starter Life
-
163
Emission Control Failure
-
165
Low Engine Power Available
-
175
Electronic Expansion Valve
-
176
Check Evap Pressure Sensor
-
177
Check Tank Pressure Sensor
-
178
Low CO2 Level
-
179
Check Tank Vacuum
-
188
DAS Controller Failure
-
203
Display Return Air Sensor
What to look at first
- Faulty return-air temperature sensor
- Return-air sensor harness or connector issue
- Sensor misplaced / poor airflow over the probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
204
Display Discharge Air Sensor
What to look at first
- Faulty discharge-air temperature sensor
- Discharge sensor harness open/short
- Sensor seeing recirculation or blocked supply
Common mistake: Controller replacement before the sensor and harness are proven.
-
216
DAS Digital Input Failure
-
233
REB switching off
-
234
Humidity Sensor
-
235
High Engine Coolant Temperature Check
-
250
DAS Reset Clock
What to look at first
- Clock not initialized or lost time
- Backup battery failed
- Controller clock circuit fault
Common mistake: Treating a maintenance/info code as a hard shutdown fault.
-
251
REB Configuration Mismatch
-
252
AFAED Operation Failure
-
253
On back up battery, alarms disabled
-
507
Check Digital Scroll Output Circuit
-
508
Speed Request Communications Error
-
509
ECU Failed to Enable
-
510
ECU Run Signal Failed
-
511
ECU Wait to Start Expired
-
512
High Compressor Suction Pres
-
513
Low Compressor Pressure Ratio
-
514
Low Compr Disch Pressure
-
515
Discharge Superheat Temp Fault
-
516
Internal Controller Comm Fault
-
517
Water in Fuel
-
518
Generator Ground Fault
-
519
Battery Charger Input Voltage Out of Range
-
520
Battery Charger Output Fault
-
521
Battery Charger Overheat Shutdown
-
522
Temperature Sensor for Unit Battery has Failed
-
523
Unit Battery Exceeded High Temperature Limit
-
524
Generator Operational Limit, Vout to Frequency Ratio
-
525
Generator Frequency Range Fault
-
526
Generator Operational Limit, Output Current
-
528
Failed J1939 CAN Communication between Controller and Battery Charger
-
529
Check Fuel Pump Circuit
-
530
Low Pressure Differential
-
531
Check Economizer Pressure Sensor
-
538
Engine J1939 CAN Datalink Degraded
-
539
Engine J1939 CAN Datalink Failed
-
540
Illegal Engine Operating State
-
542
Battery Charger Fault, Unit Forced to Low Speed
-
543
Battery Charger Internal Short
-
544
Battery Charger External Short
-
545
Battery Charger Output DC Voltage Exceeded Limit Overvoltage
-
546
Battery Charger Operating Bulk Voltage Out of Range
-
547
AC Bus Phase Loss
-
548
Battery Charger Temperature Below Operating Range.
-
549
Battery Charger Input AC Overvoltage
-
550
Battery Charger Internal Overvoltage Fault
-
551
Battery Charger Internal Temperature Sensor Fault
-
552
Battery Charger Charging, Low Battery
-
553
Battery Charger Operating Derated Due to High Temperature Conditions
-
555
Generator Loss of Phase
-
559
Engine Out of Fuel
-
560
Maximum Number of Out of Fuel Cranking Attempts have been Reached
-
599
Engine Service Tool Connected
-
600
Check Crankshaft Speed Sensor
-
601
Check Camshaft Speed Sensor
-
602
Check Throttle Position Sensor
-
603
Check Exhaust Pressure Sensor
-
604
Check Coolant Temp Sensor
-
605
Check Fresh Air Temp Sensor
-
607
Check Fuel Temp Sensor
-
608
Check Rail Pressure Sensor
-
609
Check Intake Pressure Sensor
-
610
Check Atmospheric Pressure Sensor
-
611
Check Glow Plug Circuit
-
612
Check Intake Throttle Circuit
-
613
Check Injectors
-
614
Check High Pressure Pump
-
615
Rail Pressure Fault
-
616
Engine Over Speed
-
617
Internal ECU Fault
-
618
Check EGR
-
619
ECU Main Relay Fault
-
620
No RPM Detected During Start Attempt
-
623
TRU CAN Message Timeout
-
624
Check EGR Temp Sensor
-
625
Check Intake Air Temp Sensor
-
626
Check Exhaust Temp Sensor
-
627
Exhaust Temperature out of Tolerance
-
699
Unknown ECU Fault
-
800
Crankshaft Position Sensor Error
-
801
Camshaft Speed Sensor Error
-
804
Engine Coolant Temperature Sensor Error
-
807
Fuel Temperature Sensor Error
-
808
Rail Pressure Sensor Error
-
809
Intake Air Pressure Sensor Error
-
810
Atmospheric Pressure Sensor Error
-
811
Glow Plug Circuit Error
-
813
General Injector Error
-
815
Fuel Pressure Regulation Error
-
817
Internal ECU Error
-
818
EGR Valve Actuator Error
-
819
ECU Power Relay Error
-
820
Main ECU Relay Error
-
821
Engine Timing Belt Change Required
-
825
T1 Air Intake Temperature Sensor Error
-
826
T2 Air Intake Temperature Sensor Error
-
827
EGR Valve Position Sensor Error
-
828
Lambda System Error
-
829
Engine Communication Error
-
830
Air Flow Meter Error
-
831
Oil Pressure Sensor Defective
-
832
Engine Sensor Power Supply Error
-
833
High Pressure Pump Fuel Metering Unit Error
-
834
Water in Fuel Sensor Error
-
836
Major ECU Failures
-
838
Air Intake System Error
-
839
Engine Speed Error
-
840
Fuel Injection Energizing Error
-
841
High Pressure Pump Wear
-
842
Engine Running in Safe Mode, Low Speed
-
843
Fuel Injection System Error
-
844
Failed To Crank
-
845
Starter Relay Error
-
846
T50 Switch Error
-
847
Variant Coding Error
-
854
Engine Protection Self Shutdown
Carrier truck units
The AL codes on Supra and other truck units.
-
AL0
Low oil pressure
-
AL1
High coolant temperature
-
AL2
High discharge pressure
-
AL3
Start fail
-
AL4
Low battery voltage
-
AL5
High battery voltage
-
AL6
Defrost override
-
AL7
No alternator auxiliary output
-
AL8
Starter motor fault
-
AL9
Return air sensor
-
AL10
Supply air sensor
-
AL11
Coolant temperature sensor
-
AL12
High discharge temperature
-
AL13
Discharge temperature sensor fault
-
AL14
Standby motor overload
-
AL15
Fuse open
-
AL16
System check
-
AL17
Display
-
AL18
Maintenance hour meter 1
-
AL19
Maintenance hour meter 2
-
AL20
Main compartment out of range
-
AL21
Remote compartment 2 out of range
What to look at first
- Compartment 2 return air (CD16 2RA) has moved outside the out-of-range tolerance (Function T RANGE) from its setpoint
- Compartment 2 doors open, warm product loaded, or the load blocking the remote evaporator's airflow
- Compartment 2 remote evaporator not cooling or heating: iced coil, evaporator fan not running, or its cool/heat relay (2CR/2HR) not switching
- Compartment 2 return-air sensor reading wrong
Common mistake: A refrigeration fault first: on a multi-temp unit this is a temperature alarm for compartment 2, not a component failure. Prove the box is really out of range before chasing parts.
-
AL22
Remote compartment 3 out of range
What to look at first
- Compartment 3 return air (CD17 3RA) has moved outside the out-of-range tolerance (Function T RANGE) from its setpoint
- Compartment 3 doors open, warm product loaded, or the load blocking the remote evaporator's airflow
- Compartment 3 remote evaporator not cooling or heating: iced coil, evaporator fan not running, or its cool/heat relay (3CR/3HR) not switching
- Compartment 3 return-air sensor reading wrong
Common mistake: A refrigeration fault first: on a multi-temp unit this is a temperature alarm for compartment 3, not a component failure. Prove the box is really out of range before chasing parts.
Carrier Xarios
The codes on the Xarios unit's plate.
-
AL00
No malfunction
What to look at first
Unit in operation.
- No malfunction indicated on the Red LED table
Common mistake: Chasing a fault that isn’t there, confirm code on the plate/HMI first.
-
AL01
Low pressure switch open
What to look at first
Low-side protection trip.
- Low refrigerant charge or leak
- LP switch open or out of calibration
- Restriction on the low side
Common mistake: Bad compressor before charge and the LP switch circuit are proven.
-
AL02
High pressure switch open
What to look at first
High-side protection trip.
- Blocked or dirty condenser
- Condenser fan failure
- Overcharge or non-condensables
Common mistake: Bad compressor before condenser airflow and the HP switch are proven.
-
AL03
Standby compressor over heated
What to look at first
Electric standby compressor hot.
- Poor condenser airflow on standby
- Low refrigerant charge
- Standby compressor overload or internal protector
Common mistake: Road-clutch faults, this is standby compressor overheat on electric.
-
AL04
Clutch compressor fault
What to look at first
- Clutch coil open or short
- Worn clutch or air gap out of spec
- Supply or earth fault to the clutch
Common mistake: Standby contactor issues, this is the road clutch circuit.
-
AL05
Contactor fault
What to look at first
- Welded or worn contactor contacts
- Open coil
- Control-circuit voltage missing
Common mistake: Compressor mechanical failure before contactor coil/contacts are proven.
-
AL06
Condenser fault
What to look at first
- Condenser fan motor failed
- Blocked or dirty condenser coil
- Fan wiring or relay fault
Common mistake: Low charge first, prove condenser fan and coil airflow.
-
AL07
Evaporator fan fault
What to look at first
- Evaporator fan motor failed
- Ice or debris locking the wheel
- Fan wiring or relay fault
Common mistake: Box sensor fault before the evaporator fan is proven turning and powered.
-
AL08
Hot water solenoid fault
What to look at first
- Solenoid coil open or short
- Valve stuck
- Supply or earth fault
Common mistake: Refrigeration leak path, this is the hot-water solenoid circuit.
-
AL09
Defrost valve (HGS1) fault
What to look at first
- HGS1 coil open or short
- Valve stuck closed or leaking
- Wiring fault
Common mistake: HGS2 fault, this code is HGS1 (defrost valve).
-
AL10
Liquid injection valve fault
What to look at first
- Injection-valve coil open or short
- Valve stuck
- Wiring fault
Common mistake: Liquid solenoid (AL19), this is liquid injection.
-
AL11
Hot gas valve (HGS2) fault
What to look at first
- HGS2 coil open or short
- Valve stuck closed or leaking
- Wiring fault
Common mistake: HGS1 fault, this code is HGS2 (hot gas).
-
AL12
High temperature alarm
What to look at first
Box too warm vs limits.
- Loss of cooling capacity
- Door open or poor airflow
- Setpoint or probe error
Common mistake: Probe fault before doors, airflow, and real cooling are proven.
-
AL13
Low temperature alarm
What to look at first
Box too cold vs limits.
- Unit not terminating cool
- Setpoint too low
- Probe error
Common mistake: Probe fault before setpoint and heat/defrost mode are proven.
-
AL14
Defrost alarm > 45 minutes
What to look at first
Stuck in defrost too long.
- HGS1/HGS2 not opening
- Defrost termination probe fault
- Heavy ice load / poor airflow
Common mistake: Leaving it in defrost hoping it finishes, prove valves and termination.
-
AL15
Setpoint adjusted out of the range -29°C / +30°C
What to look at first
Setpoint outside -29°C / +30°C.
- Setpoint entered outside -29°C to +30°C
- Controller configuration mismatch
Common mistake: Refrigeration fault, this is setpoint out of allowed range.
-
AL16
Drain water resistor fault
What to look at first
- Drain-water resistor open or short
- Wiring or connector fault
- Controller output fault
Common mistake: Drain blockage only, prove the resistor element and supply.
-
AL17
Thermal break down standby transformer or diode bridge protection fault
What to look at first
- Standby transformer overheated
- Diode-bridge protection open
- Standby supply fault or overload
Common mistake: Road engine faults, this is standby transformer / diode bridge protection.
-
AL18
Electrical heating relay fault
What to look at first
- Heating relay coil open or contacts welded
- Heater circuit overload
- Wiring fault
Common mistake: Hot-gas heat path, this is the electrical heating relay.
-
AL19
Liquid solenoid valve fault
What to look at first
- Liquid-solenoid coil open or short
- Valve stuck closed or leaking
- Wiring fault
Common mistake: Liquid injection (AL10), this is the liquid solenoid.
-
AL20
LP standby pressure switch opened
What to look at first
Standby low-side protection.
- Low charge on standby
- Standby LP switch open or out of calibration
- Restriction on the low side
Common mistake: Road LP switch (AL01) without checking standby LP switch circuit.
-
AL21
Open circuit contactor compressor
What to look at first
- Open coil or broken wire to the compressor contactor
- Connector unplugged
- Controller output open
Common mistake: Motor windings first, prove open in the contactor control/sense circuit.
-
AL22
Open circuit condenser fan
What to look at first
- Open condenser-fan motor or wiring
- Connector unplugged
- Controller output open
Common mistake: Dirty coil first on an open-circuit code, prove the fan circuit continuity.
-
AL23
Open circuit hot water solenoid
What to look at first
- Open solenoid coil or wiring
- Connector unplugged
- Controller output open
Common mistake: Stuck valve before open-circuit coil/wiring is proven.
-
AL24
Open circuit defrost valve (HGS1)
What to look at first
- Open HGS1 coil or wiring
- Connector unplugged
- Controller output open
Common mistake: HGS2 open, this is HGS1 open-circuit.
-
AL25
Open circuit liquid injection valve
What to look at first
- Open injection-valve coil or wiring
- Connector unplugged
- Controller output open
Common mistake: Injection valve stuck before open-circuit is proven.
-
AL26
Open circuit hot gas valve (HGS2)
What to look at first
- Open HGS2 coil or wiring
- Connector unplugged
- Controller output open
Common mistake: HGS1 open, this is HGS2 open-circuit.
-
AL27
Open circuit drain water resistor (DWR1)
What to look at first
- Open DWR1 element or wiring
- Connector unplugged
- Controller output open
Common mistake: Drain blockage before DWR1 open-circuit is proven.
-
AL28
Open circuit electrical heating relay (EHR)
What to look at first
- Open EHR coil or wiring
- Connector unplugged
- Controller output open
Common mistake: Heater element first, prove EHR open-circuit sense.
-
bAt
Battery low voltage alarm
What to look at first
Battery voltage low.
- Discharged or failing battery
- Poor charging on road or standby
- Corroded terminals or high resistance earth
Common mistake: Alternator only, measure voltage and terminals before condemning charge source.
-
EE
Evaporator temperature probe open circuit
What to look at first
- Evaporator probe open-circuit
- Broken wire or unplugged connector
- Probe out of range
Common mistake: Box air probe, this is the evaporator temperature probe open circuit.
-
Err
Programming mistake of the maximum setpoint by the user
What to look at first
- Maximum setpoint programmed outside the allowed range
- User configuration error
Common mistake: Unit refrigeration fault, this is a user max-setpoint programming mistake.
Carrier APX
Plain numbers on the APX display, and the five-figure engine and control faults.
-
1
Low Fuel Level Warning
What to look at first
- Low fuel level
- Fuel level sender fault
- Fuel delivery restriction (filter/air)
Common mistake: Fuel pump failure before level, filters, and sender are proven.
-
2
Low Engine Oil Level Warning
-
3
Low Coolant Level
What to look at first
- Low coolant level
- Coolant level sensor/switch fault
- External leak at radiator/hoses/pump
Common mistake: Bad coolant sensor before level, radiator face, and pump are proven.
-
4
Low Refrigerant Level
-
11
Check/Low Engine Oil Pressure
-
12
High coolant temperature
What to look at first
Cool the unit before you dig deeper.
- Low coolant level or air in the cooling system
- Blocked radiator / poor radiator airflow
- Failed water pump, stuck thermostat, or fan issue
Common mistake: Bad coolant temp sensor before level, radiator face, and pump/fan are proven.
-
13
High discharge pressure
What to look at first
Protect the compressor, fix airflow first.
- Blocked or dirty condenser / poor airflow
- Condenser fan not running
- Overcharge or non-condensables (prove with gauges after airflow is clean)
Common mistake: Bad HP transducer before condenser airflow and fan are proven.
-
14
High A/C Amps
-
15
Battery Voltage Too High
-
16
Battery voltage too low
What to look at first
Prove charging and connections.
- Discharged or failing battery
- Alternator / charger not charging (see also alarm 51)
- Corroded terminals or high-resistance earth
Common mistake: This is ‘too high’ (that’s code 15), measure before you swap parts.
-
17
High compressor discharge temperature
What to look at first
Shut down and prove charge/airflow.
- Low refrigerant charge
- Condenser airflow restriction / fan fault
- Faulty discharge temperature sensor
Common mistake: Compressor replacement before charge, condenser airflow, and the CDT sensor are proven.
-
18
Low refrigerant pressure
What to look at first
Find the leak or restriction, don’t just top up blind.
- Refrigerant leak / undercharge
- Restricted filter-drier or liquid line
- Expansion device stuck closed / LP sensor fault
Common mistake: ‘Just add gas’ before you’ve leak-checked and proven the low-side circuit.
-
19
Low Fuel Shutdown
What to look at first
- Low fuel level
- Fuel level sender fault
- Fuel delivery restriction (filter/air)
Common mistake: Fuel pump failure before level, filters, and sender are proven.
-
20
Maximum Compr Alarms
-
21
Technician Reset Required
-
22
Low Suction Superheat
-
23
A/C Current Over Limit
-
24
Compression Ratio Exceeded
-
27
High Suction Pressure
-
28
Check refrigeration system
What to look at first
Capacity or mode isn’t matching what the box needs.
- Charge / capacity problem
- Valve or mode (cool/heat/defrost) not doing what the controller commanded
- Sensor readings out of range misleading the control
Common mistake: One failed part, prove setpoint, sensors, airflow, then refrigeration path.
-
29
Check Heat Cycle
-
30
Failed To Run Min Time
-
31
Failed To Start – Auto Mode
-
32
Failed To Start – Manual
-
34
Engine Failed to Stop
-
35
Check Starter Circuit
-
36
Check Coolant Temp
What to look at first
- Faulty coolant temperature sensor
- Sensor harness open/short
- Actual cooling-system issue reflecting on the sensor
Common mistake: Bad coolant sensor before level, radiator face, and pump are proven.
-
37
Check Low Speed RPM
-
38
Check High Speed RPM
-
39
Check Engine RPM
-
40
Check Engine Preheat Circuit
-
41
Engine Stalled
-
51
Alternator (battery charger) not charging
What to look at first
Battery will die on the road.
- Broken/loose belt or failed alternator
- Corroded battery terminals / poor earth
- Wiring or regulator fault
Common mistake: ‘Just a low battery’ (code 16) without measuring charge voltage with the unit running.
-
53
Box temperature out of range
What to look at first
Product risk; prove cooling then sensors.
- Loss of cooling capacity or long door-open
- Setpoint / mode wrong for the load
- Box or return-air sensor reading wrong
Common mistake: Sensor fault before you’ve confirmed the unit is actually refrigerating.
-
54
Defrost Not Complete
-
55
Check Defrost Air Switch
-
56
Check Evaporator Air Flow
What to look at first
- Restricted evaporator airflow / icing
- Evaporator fan not running at commanded speed
- Blocked return or discharge path
Common mistake: Charge top-up before evaporator airflow and fan are proven.
-
57
Check Remote Switch 1
-
59
Datalogger Not Recording
-
60
Datalogger Time Wrong
-
61
Door Open
What to look at first
- Door left open beyond timeout
- Door switch stuck or misadjusted
- Door-switch wiring fault
Common mistake: Cargo claim before door switch and actual door events are proven.
-
62
C2 Box Temp Out of Range
-
63
C3 Box Temp Out of Range
-
71
Bad F2 or F3 Fuse
-
72
Bad F4 or F6 Fuse
-
73
No A/C Power – Check Cord
-
74
AC Phase Reversed
What to look at first
- Incoming phase rotation incorrect
- Phase-sensing circuit fault
- Site power wiring error
Common mistake: Motor rewind before phase rotation and supply voltage are proven.
-
75
Compressor Motor Overload
-
76
Condenser Motor Overheated
-
77
Evap Motor Overheated
-
78
Check SV1 Circuit
-
79
Check SV4 Circuit
-
80
Check SV3 Circuit
-
81
Check FHR Circuit
-
82
Check Remote Out of Range Light
-
83
Check Remote Defrost Light
-
84
Check Remote Alarm Light
-
85
Check UL1 Circuit
-
86
Check UL2 Circuit
-
87
Check Remote Heat Light
-
88
Check Remote Cool Light
-
89
Check Remote Auto Light
-
90
Check AFA Solenoid Circuit
-
91
Check 1HTCON1 Relay Coil
-
92
Check 1HTCON2 Relay Coil
-
93
Check Start Up Buzzer
-
94
Check Comp Contactor 1
-
95
Check CDCON Relay Coil
-
96
Check GENCONR Relay Coil
-
97
Check SV2 Circuit
-
98
Check High Temperature Thermostat
-
99
Check Standby Contactor
-
100
Overload/Ground Fault
-
101
C2 Evap Motor Overheated
-
102
C3 Evap Motor Overheated
-
103
Check 2HTCON1 Relay Coil
-
104
Check 2HTCON2 Relay Coil
-
105
Check 3HTCON1 Relay Coil
-
106
Check 3HTCON2 Relay Coil
-
107
Check 2LSV Circuit
-
108
Check 3LSV Circuit
-
109
Check 1EVCON Relay Coil
-
110
Check 2EVCON Relay Coil
-
111
Check 3EVCON Relay Coil
-
112
Check Bypass Circuit
-
113
Check Economizer Circuit
-
114
Check LIV Circuit
-
117
Check DCR2 Circuit
-
121
Check Ambient Air Sensor
What to look at first
- Open/short or high-resistance ambient sensor
- Damaged ambient sensor harness or connector
- Sensor reading out of expected ambient range
Common mistake: Controller replacement before the sensor and harness are proven.
-
122
Check Return Air Sensor
What to look at first
- Faulty return-air temperature sensor
- Return-air sensor harness or connector issue
- Sensor misplaced / poor airflow over the probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
123
Check Supply Air Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
124
Check Defrost Termination 1 Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
125
Check Comp Discharge Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
126
Check Fuel Sensor Circuit
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
127
Check Suction Temp Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
128
Low/Unbalanced A/C Amps
-
129
Check Engine Coolant Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
130
Check Engine RPM Sensor
What to look at first
- RPM sensor failed or air-gapped incorrectly
- RPM sensor harness open/short
- Actual engine speed problem (prove sensor first)
Common mistake: Controller replacement before the sensor and harness are proven.
-
131
Check Evap Temp Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
132
Check Defrost Termination 2 Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
133
Check Remote Temp Sensor 1
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
134
Check Remote Temp Sensor 2
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
135
Check Remote Temp Sensor 3
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
136
C2 Check Supply Air Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
137
C2 Check Return Air Sensor
What to look at first
- Faulty return-air temperature sensor
- Return-air sensor harness or connector issue
- Sensor misplaced / poor airflow over the probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
138
C3 Check Return Air Sensor
What to look at first
- Faulty return-air temperature sensor
- Return-air sensor harness or connector issue
- Sensor misplaced / poor airflow over the probe
Common mistake: Controller replacement before the sensor and harness are proven.
-
139
C2 Check Defrost Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
140
C3 Check Defrost Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
223
Engine Maintenance Due
-
224
Standby Maintenance Due
-
225
General Maintenance Due
-
226
Service Soon PM 1 Due
-
227
Service Soon PM 2 Due
-
228
Service Soon PM 3 Due
-
229
Service Soon PM 4 Due
-
230
Service Soon PM 5 Due
-
232
Setpoint Error
-
233
Model # Error
-
237
Function Parameter Error
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
238
Configurations Error
-
242
Dis Press Calibrate Error
-
243
Suct/Evap Calibrate Error
-
244
Econo Calibrate Error
-
245
Can Not Save Setting
-
246
EEPROM Write Failure
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
248
Config Mode / HP2 Error
-
255
Microprocessor Error
What to look at first
- Controller memory/firmware fault
- Power interruption during write
- Controller hardware failure
Common mistake: Flashing firmware before power integrity and connectors are proven.
-
2000
Update Software
-
2001
Rear Panel Shutdown Requested
-
2002
Low Discharge Superheat
-
2003
Display Module Error
-
3000
Motor Overload 1
-
3001
Engine Load Calibration
-
3002
Check Clutch Slip
-
4000
Check Remote Switch 3
-
4001
Check Remote Switch 4
-
4002
High Economizer Superheat
-
4004
No Setpoint Change
-
4005
No Setpoint Change C2
-
4006
No Setpoint Change C3
-
5002
Fuel Pump Relay
-
5003
Diesel / Electric Relay
-
5004
Bad F13 Fuse
-
5005
Bad F9 Fuse
-
5006
Bad F5 Fuse
-
5007
Bad F3 Fuse
-
5008
Bad F10 Fuse
-
5009
Check Standby Contactor 1
-
5010
Check Standby Contactor 2
-
5011
Check High Speed Control Circuit
-
5012
Check ENSCU Power Circuit
-
5013
Check Clutch Circuit
-
5014
Check Starter Solenoid Circuit
-
5015
Check Hot Gas Valve Circuit
-
5016
Check Remote Amber Light
-
5017
Check Eng Preheat Enable Circuit
-
5018
Check Power Enable Control
-
5019
Check CDCON Relay Coil Two
-
5020
Check Htr Cntr One
-
5021
Check Htr Cntr Two
-
5022
C2 Check High Temp Thermostat
-
5023
C3 Check High Temp Thermostat
-
5024
Check Standby Contactor
-
5025
Check Standby Contactor
-
6000
Cond. Motor 2 Overheated
-
6001
Check Light Bar
-
7000
Economizer Temp Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
7001
Economizer Press Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
7002
C3 Chk Supply Air Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
7003
C2 Chk Evap Temp Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
7004
C3 Chk Supply Air Sensor
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
7006
Suction Pressure Sensor
What to look at first
- Suction pressure sensor failed
- Sensor harness open/short
- Actual low-side pressure anomaly
Common mistake: Controller replacement before the sensor and harness are proven.
-
20100
No Comm From Micro to Display
-
20101
No Comm From Micro to Remote Display
-
21100
No Comm From Any Board to Main Micro
-
22100
No Comm From Micro to INPBD1
-
22101
Sensor Input Voltage Low INP1
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
22102
Sensor Input Voltage High INP1
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
22103
Output Lost Configuration
-
23100
No Comm From Micro to Outbd1
-
23101
Output Lost Configuration
-
24100
No Comm From Micro to CCB1
-
24101
Sensor Input Voltage Low CCB1
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24102
Sensor Input Voltage High CCB1
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24200
No Comm From Micro to CCB2
-
24201
Sensor Input Voltage Low CCB2
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24202
Sensor Input Voltage High CCB2
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24300
No Comm From Micro to CCB3
-
24301
Sensor Input Voltage Low CCB3
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24302
Sensor Input Voltage High CCB3
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24400
No Comm From Micro to CCB4
-
24401
Sensor Input Voltage Low CCB4
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
24402
Sensor Input Voltage High CCB4
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
25100
No Comm From Micro to STP1
-
25101
Over Current STP1
-
25102
Check Input Voltage STP1
-
25200
No Comm From Micro to STP2
-
25201
Over Current STP2
-
25202
Check Input Voltage STP2
-
25300
No Comm From Micro to STP3
-
25301
Over Current STP3
-
25302
Check Input Voltage STP3
-
25400
No Comm From Micro to STP4
-
25401
Over Current STP4
-
25402
Check Input Voltage STP4
-
26100
No Comm From Micro to ENCU
-
26101
Engine Over Heat ENCU
-
26102
Water Temp Low ENCU
-
26103
Water Temp High ENCU
-
26104
Battery Voltage High ENCU
-
26105
Engine Overrun ENCU
-
26106
Sensor Supply Voltage 1 Low ENCU
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
26107
Oil Pressure Error ENCU
-
26108
Rack Position Abnormal ENCU
-
26109
Actuator Abnormal ENCU
-
26110
Engine Speed Sensor ABN ENCU
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
26111
Intake Air Pressure Low ENCU
-
26112
Intake Air Pressure High ENCU
-
26201
EES Service Required
-
26202
EES High Back Pressure
-
26203
EES Low Back Pressure
-
26204
EES ECU Voltage Low
-
26205
EES Filter Inlet Temp
-
26206
EES Check Fuel Pump Circuit
-
26207
EES Check Air Control Valve
-
26208
EES Check Fuel Injector Circuit
-
26209
EES Filter Outlet Temp
-
26210
EES Exhaust Inlet Temp
-
26211
EES ECU Output Failure
-
26212
EES ECU Log Failure
-
26213
EES ECU Clock Failure
-
26214
EES ECU Temp Low
-
26215
EES ECU Temp High
-
26216
EES No Temperature Rise
-
26217
EES System Failure
-
26218
EES System Overtemp
-
26219
Temp Sensor Drift
What to look at first
- The sensor open/short or out of range
- Sensor harness/connector fault
- Sensor reading inconsistent with conditions
Common mistake: Controller replacement before the sensor and harness are proven.
-
26220
EES Back Pressure Exceeded
-
26221
EES Frequent Regenerations
-
26222
EES Back Pressure Offset Exceeded
-
27100
No Comm from Micro to Comm Module
-
27200
No Comm from Micro to Optional Comm Module