Sensor Failure (Probe, Thermistor, Transducer)
312 related codes
Temperature probe, return-air sensor, ambient sensor or pressure transducer reading out of range, open or shorted. Sensor swap is often the fastest fix.
Low Fuel Level Warning
Indicates that the fuel level is below the minimum safety threshold.
Low Engine Oil Level Warning
The sensor detects an engine oil level insufficient for prolonged operation.
Low Refrigerant Level
Lack of refrigerant in the system's refrigeration circuit.
Alarm 10 – Supply Air Temperature Sensor (SATS) Out of Range
Carrier Transicold alarm AL10 (Alarm Code 10) means the Advance microprocessor has detected the Supply Air Temperature Sensor (SATS/STS) reading is out of range, open, or shorted. The SATS lives in the discharge airstream after the evaporator on Vector, X4, X2 and Supra reefer units and is the primary control sensor when 'Supply' is selected. When AL10 latches, the controller falls back to the Return Air Sensor and box temperature control becomes unstable — a frequent cause of load-quality claims.
Check/Low Engine Oil Pressure
Engine oil pressure is dangerously low, triggering unit shutdown.
High A/C Amps
High electrical current detected in AC system components.
Battery Voltage Too High
The system detects a battery voltage exceeding 15.5V DC.
Alarm 17 – High Compressor Discharge Temperature (CDT)
Carrier Transicold alarm code 17 (AL17) triggers when Compressor Discharge Temperature (CDT) climbs above the safety threshold — typically 310°F (154°C) on Vector, X4, X2 and Supra reefer units. The Advance controller shuts the unit down to protect the compressor from thermal breakdown of oil, valve plate damage, and burned windings. AL17 almost always points at a refrigerant-side or airflow problem, not the compressor itself.
Low Refrigerant Press
Refrigerant pressure too low for safe operation.
Low Fuel Shutdown
Unit shut down because fuel level reached zero.
High Suction Pressure
Suction pressure higher than allowed limit for the engine.
Check Heat Cycle
Hot gas heating cycle failure.
Engine Failed to Stop
The engine does not shut down when the controller sends the signal.
Check Starter Circuit
Anomaly detected in the starter motor electrical circuit.
Check Coolant Temp
Engine temperature is not rising or is out of expected range.
Check Low Speed RPM
Engine RPM at low speed is incorrect.
Check High Speed RPM
Engine RPM at high speed is incorrect.
Check Engine RPM
The engine is not reaching or maintaining the required RPM for the operating cycle.
Box Temp Out of Range
The temperature inside the box is outside the established tolerance range relative to the setpoint.
Defrost Not Complete
The defrost cycle has exceeded the maximum allowed time without completing correctly.
Check Defrost Air Switch
Failure detected in the air pressure switch that initiates or monitors defrost.
Check Remote Switch 1
Fail in the remote switch 1 circuit, usually related to door sensors or auxiliary switches.
Check Remote Switch 2
Failure in the remote switch 2 circuit, typically tied to a door sensor or auxiliary input. Close all compartment doors; if the unit remains shut down, repair immediately.
Door Open
The sensor indicates a compartment door is open, stopping the unit.
C3 Box Temp Out of Range
Third compartment (C3) temperature is outside allowable limits.
Bad F2 or F3 Fuse
Failure in fuses F2 or F3 which control vital accessory power circuits.
Bad F4 or F6 Fuse
Failure detected in fuses F4 or F6, affecting control or lighting circuits.
AC Phase Reversed
External AC power phase is reversed, which can damage motors.
Condenser Motor Overheated
The condenser fan motor thermal sensor reports excessive temperature.
Evap Motor Overheated
The evaporator fan motor is operating above its safe temperature threshold.
Check SV1 Circuit
Failure detected in the SV1 solenoid valve electrical circuit.
Check SV4 Circuit
Failure detected in the SV4 solenoid valve electrical circuit.
Check FHR Circuit
Failure in the Fuel Heater Relay (FHR) or heater circuit.
Check Remote Defrost Light
Electrical issue detected in the remote Defrost indicator light circuit.
Check UL2 Circuit
Electrical failure detected in the Compressor Unloader 2 (UL2) circuit.
Check Remote Cool Light
A problem has been detected in the remote cooling indicator light (Cool Light) circuit.
Check Remote Auto Light
Failure detected in the remote automatic mode light circuit (Auto Light).
Check 1HTCON2 Relay Coil
Failure in the 1HTCON2 relay coil (Heating Contactor 2).
Check CDCON Relay Coil
Failure in the CDCON relay coil (Condenser Fan).
Check GENCONR Relay Coil
Failure in the GENCONR relay coil (Generator Contactor).
Check High Temperature Thermostat
Activation of the high temperature thermostat (Overheat protection).
Check Standby Contactor
Failure in the electric standby mode contactor coil or circuit.
Overload/Ground Fault
Electrical overload or ground fault detected in the system.
Check 2HTCON1 Relay Coil
Failure in the 2HTCON1 relay coil (Compartment 2 Heat 1).
Check 3LSV Circuit
Issue in the Liquid Line Solenoid Valve 3 (3LSV) circuit.
Check 1EVCON Relay Coil
Fault in the evaporator motor contactor 1 (1EVCON).
Check Bypass Circuit
Problem detected in the bypass solenoid valve circuit.
Check Ambient Air Sensor
Ambient air temperature sensor failure.
Check Return Air Sensor
Failure in the return air temperature sensor.
Check Supply Air Sensor
Fault detected on the supply air temperature sensor (SAS). If the unit shut down, repair immediately; otherwise report and repair at end of trip.
Check Defrost Termination 1 Sensor
Defrost termination sensor 1 detects an out-of-range or open circuit condition.
Check Comp Discharge Sensor
An abnormal reading is detected at the compressor discharge temperature sensor.
Check Fuel Sensor Circuit
Failure in the fuel level sensor circuit.
Check Suction Temp Sensor
Failure in the suction temperature sensor circuit.
Check Engine Coolant Sensor
Failure in the engine coolant temperature sensor.
Check Engine RPM Sensor
Signal loss or incorrect reading from the diesel engine RPM sensor.
Check Evap Temp Sensor
Failure detected in the evaporator coil temperature sensor.
Check Defrost Termination 2 Sensor
Failure in the secondary defrost termination sensor (DTS2).
Check Remote Temp Sensor 1
Signal error in remote temperature sensor number 1.
Check Remote Temp Sensor 2
Signal error in remote temperature sensor number 2.
Check Remote Temp Sensor 3
Signal error in remote temperature sensor number 3.
C2 Check Supply Air Sensor
Supply air sensor error for compartment 2 (C2).
C2 Check Return Air Sensor
Return air sensor error for compartment 2 (C2).
C3 Check Return Air Sensor
Return air sensor error for compartment 3 (C3).
C2 Check Defrost Sensor
Defrost sensor error for compartment 2 (C2).
C3 Check Defrost Sensor
Defrost sensor error for compartment 3 (C3).
Pretrip Stopped By User
The Pretrip test was manually canceled by the operator.
C2 Check Heater 1 Circuit
Failure in compartment 2 (C2) heater 1 circuit.
Check SV4 Circuit
Failure in solenoid valve 4 (SV4) circuit.
Check Eng Preheat Enable Circuit
Failure in the engine preheat enable circuit.
Check Return Air Sensor
Critical error in the return air sensor during Pretrip.
Check Supply Air Sensor
Critical error in the supply air sensor during Pretrip.
Check Coolant Temp Sensor
Engine coolant temperature sensor failure detected during Pretrip.
Check Battery Current
Battery current reading is outside expected parameters during testing.
Check Ambient Air Sensor
Ambient air temperature sensor reports erratic values or is disconnected.
Check Defrost Term 1 Sensor
Failure in defrost termination sensor number 1.
Check Disch Temp Sensor
Compressor discharge temperature sensor out of range.
Check Suction Temp Sensor
Compressor suction temperature sensor is not responding correctly.
C3 Check Heater 1 Circuit
Failure in heating circuit 1 for compartment 3.
C2 Chk Supply Air Sensor
Failure in the compartment 2 supply air sensor.
System Not Equalized
System pressures did not equalize after the timeout period.
Check Bypass
Generic or flow failure in the bypass valve detected by pressure sensors.
Check Economizer
Economizer performance is insufficient or null.
Check Low Speed RPM
Engine revolutions at low speed are out of range.
Check Evap Superheat
Evaporator superheat is outside design limits.
Check UL1
Circuit failure for cylinder unloader number 1 (UL1).
Check SV4 Valve
Failure in the circuit of solenoid valve SV4 (Hot Gas/Bypass Valve).
Check SV1 Valve
Failure in the solenoid valve SV1 circuit.
C2 Check Evap Fan Motor
Fault detected in the compartment 2 evaporator fan motor.
Check Evap Outlet Temp
The evaporator outlet temperature sensor does not respond correctly during tests.
Check Heater 2 Circuit
Fault detected in the Heater 2 circuit, preventing effective defrost or heating.
Check Evap Fan Motor
General evaporator fan motor error detected during self-inspection.
Check UL2
Electrical fault detected in the Unloader 2 (UL2) solenoid circuit.
Low Discharge Pressure
Insufficient discharge pressure; the unit cannot compress effectively.
C2 Chk Return Air Sensor
Compartment 2 return air sensor with reading failures.
High Side Leak
Presumptive detection of a leak in the high-pressure side of the system.
Low Suction Pressure
Critical low suction pressure detected by the transducer.
Check Defrost Term 2 Sensor
Failure in the evaporator 2 defrost termination sensor.
Check Condenser Fan Circuit
Error in the control or power circuit of the condenser fans.
Check Generator Cont Circ
Failure in the generator contactor circuit.
C3 Chk Return Air Sensor
Failure in the return air sensor for compartment 3.
C2 Check Defrost Sensor
Failure in the compartment 2 defrost sensor.
C3 Check Defrost Sensor
Failure in the compartment 3 defrost sensor.
Check Damper – Not Open
The defrost damper is stuck in the closed position or is not opening properly.
Dis Press Calibrate Error
Calibration failure of the discharge pressure sensor; data is out of range.
Suct/Evap Calibrate Error
Calibration error in the suction or evaporator pressure sensors.
Econo Calibrate Error
Error detected in the economizer sensor calibration.
Config Mode / HP2 Error
Conflict between the selected configuration mode and the high pressure sensor (HP2).
Rear Panel Shutdown Requested
Unit shutdown requested from the rear or remote control panel.
Low Discharge Superheat
Low discharge superheat detected; risk of liquid floodback to the compressor.
Motor Overload 1
Overload detected in the electric motor or fan motor 1.
Engine Load Calibration
Failure during the diesel engine load calibration process.
Check Remote Switch 4
Failure or abnormal status detected in auxiliary remote switch 4.
High Economizer Superheat
High superheat at the economizer; reduced cooling efficiency.
Fuel Pump Relay
Fault detected in the fuel pump relay circuit.
Bad F13 Fuse
Open or defective F13 fuse; generally affects auxiliary circuits.
Bad F9 Fuse
Open F9 fuse; this fuse typically protects control circuits.
Bad F5 Fuse
Blown F5 fuse; critical for safe system operation.
Bad F3 Fuse
Open F3 fuse; affects vital control logic components.
Bad F10 Fuse
Blown F10 fuse; interrupts critical control functions.