Low Refrigerant or Leak

Low Engine Oil Level Warning

The sensor detects an engine oil level insufficient for prolonged operation.

Low Coolant Level

Engine coolant level is below recommended operating limits.

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.

High Discharge Pressure

Refrigerant discharge pressure exceeded the safety limit.

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.

Low Suction Superheat

Low suction superheat, risk of liquid floodback to compressor.

Compression Ratio Exceeded

Pressure ratio between suction and discharge out of range.

High Suction Pressure

Suction pressure higher than allowed limit for the engine.

Check Refrig System

The system detected poor cooling efficiency.

Alternator (Battery Charger) Not Charging

The alternator is not charging the unit's battery while the engine is running.

Defrost Not Complete

The defrost cycle has exceeded the maximum allowed time without completing correctly.

C2 Box Temp Out of Range

Second compartment (C2) temperature is outside allowable limits.

Compressor Motor Overload

The compressor motor overload relay has tripped due to excessive current.

Check Economizer Circuit

Failure in the economizer circuit.

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 Comp Discharge Sensor

An abnormal reading is detected at the compressor discharge temperature sensor.

Check Suction Temp Sensor

Failure in the suction temperature sensor circuit.

Check Disch Temp Sensor

Compressor discharge temperature sensor out of range.

Check Suction Temp Sensor

Compressor suction temperature sensor is not responding correctly.

Can Not Pump Down

The system failed to perform internal vacuum (Pump Down) within the established time.

Check Economizer Circuit

A problem was detected in the operation of the economizer circuit.

Check Economizer

Economizer performance is insufficient or null.

Check Evap Superheat

Evaporator superheat is outside design limits.

Check LIV

Flow or mechanical failure in the Liquid Injection Valve (LIV).

Check Suction Mod Valve

Failure in the Suction Modulation Valve (SMV).

High Suction Pressure

Excessively high suction pressure detected during diagnostic tests.

Low Suction Pressure

Suction pressure below the permitted operating limits.

High Discharge Pressure

Dangerously high discharge pressure; risk of high pressure cutout.

Low Discharge Pressure

Insufficient discharge pressure; the unit cannot compress effectively.

High Side Leak

Presumptive detection of a leak in the high-pressure side of the system.

Check Discharge Check Valve

Reported failure in the efficiency or closure of the discharge check valve.

Low Suction Pressure

Critical low suction pressure detected by the transducer.

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.

Low Discharge Superheat

Low discharge superheat detected; risk of liquid floodback to the compressor.

High Economizer Superheat

High superheat at the economizer; reduced cooling efficiency.

Suction Pressure Sensor

Fault in the suction pressure sensor of the refrigeration system.

C3 Chk Evap Outlet Temp

Error in compartment 3 evaporator outlet temperature detected during Pre-Trip.

C2 Chk Evap1 Superheat

Superheat out of range in evaporator 1 of compartment 2.

C3 Chk Evap2 Superheat

Superheat out of range in evaporator 2 of compartment 3.

Check Input Voltage STP4

Voltage detected outside tolerance at the STP4 module.

Battery Voltage High ENCU

Supply voltage to the engine control unit (ENCU) above 15.5V.

Intake Air Pressure Low ENCU

Intake manifold air pressure is below normal.

EES Low Back Pressure

Reported exhaust pressure is unusually low during normal operation.

EES Check Air Control Valve

The system detected a malfunction in the air control valve actuator or circuit.

EES Frequent Regenerations

The system requires regenerations with an abnormally high frequency.

Check (Control) Discharge Air Sensor (Zone)

Failure of the discharge air sensor, which measures the air leaving the evaporator toward the cargo.

High Evaporator Temperature (Zone)

An excessively high evaporator temperature has been detected.

High Discharge Pressure (or Temperature)

The compressor discharge pressure or temperature has exceeded safety limits.

Engine Failed to Crank

The starter motor does not turn or the engine fails to rotate for ignition.

High Engine Coolant Temperature

The diesel engine has reached a temperature above the safety limit.

Cooling Cycle Check (Zone)

The system detects insufficient cooling capacity during monitoring.

Heating Cycle Check (Zone)

The system detects insufficient heating capacity.

Cooling Cycle Fault (Zone)

Critical system failure preventing cooling; unit shuts down to protect cargo.

Heating Cycle Fault (Zone)

Critical failure preventing the unit from generating heat when required.

Refrigeration Capacity Low (Zone)

The unit or zone is not reaching the expected cooling capacity and has been stopped for safety.

Check Engine Coolant Level

The level sensor detects that the engine coolant is below the safe limit.

Unit Forced to Low Speed

The unit has restricted operation to low speed to protect the engine or system.

Unit Forced to Low Speed Modulation

The unit is forced to low speed due to a limitation in the modulation system.

Check Fuel System

The system has detected problems in fuel supply or suction.

Low Battery Voltage

The battery voltage powering the microprocessor is too low.

Low Engine Oil Level

The sensor indicates the engine oil level is below the safe limit.

High Compressor Temp

The compressor temperature is unusually high, approaching the safety limit.

High Compressor Temp Shutdown

The unit stopped to protect the compressor due to excessive temperature.

Check Discharge Pressure Sensor

The controller detected an erroneous signal from the discharge pressure sensor.

Check Suction Pressure Sensor

The controller detected an erroneous signal from the suction pressure sensor.

ETV Fault – Electronic Throttling Valve Circuit (Code 89)

Thermo King alarm code 89 indicates a failure in the Electronic Throttling Valve (ETV) control circuit. The ETV is a stepper-motor modulating valve in the suction line that regulates suction pressure and compressor loading on Thermo King SB-, SLXi, SLXe, SLX, SLX Whisper, T-Series, Precedent and TriPac reefer units. When the microprocessor cannot drive or read the ETV stepper coils correctly, it logs Code 89 and forces the unit into a protective mode — often unable to hold setpoint or pull down.

Low Compressor Suction Pressure

Dangerously low compressor suction pressure detected.

Low Fuel Level

Tank fuel level is below the preset safety limit.

High Compressor Pressure Ratio

Excessive pressure ratio detected between compressor suction and discharge, risking mechanical integrity.

Controlling on Evap Coil Outlet Temp (CR)

Unit is controlling temperature based on evaporator outlet due to a primary sensor failure.

Low Evaporator Coil Temperature (CR)

Evaporator coil temperature is dangerously low, which may lead to icing or freezing.

Check High Discharge Pressure Sensor

Error in the high discharge pressure sensor (Replaced by code 86 in newer models).

Check Suction Line Sol Circuit (Zone)

Failure in the suction line solenoid valve circuit for a specific zone.

Check High Pressure Cut Out Switch

Fault in the High Pressure Cut Out (HPCO) switch or its circuit.

Check PMW Liquid Injection Circuit

Failure in the Pulse Width Modulation (PMW) liquid injection circuit, crucial for compressor cooling.

Check Back Pressure Regulator (CR)

Indicates a problem with the suction pressure regulator or back pressure regulator, affecting temperature stability.

Low Suction Pressure Switch Failure

Inconsistent state or failure detected in the low suction pressure switch.

Check Suction/Liquid Heat Exchanger Bypass Valve

Indicates a problem with the operation of the suction/liquid heat exchanger bypass valve.

Check Evaporator Pressure Sensor (CR)

The evaporator pressure sensor is sending signals that are out of range.

Low CO2 Fuel Level (CR)

Low level of CO2 fuel detected in the storage tank.

Check Display Discharge Air Sensor (Zone)

The display discharge air temperature sensor is presenting erroneous readings.

High Compressor Suction Pressure (Scroll Only)

Excessively high suction pressure detected in Scroll-type compressors.

Low Compressor Suction Ratio (Scroll Only)

Suction pressure ratio below safe operating limits for the Scroll compressor.

Low Compressor Discharge Pressure (Scroll Only)

Scroll compressor discharge pressure too low during operation.

Minimum ETV Discharge Superheat Temp (Scroll)

ETV controlled discharge superheat is at the minimum thermal limit.

Generator Ground Fault

Current leakage to ground detected in the generator circuit.

Check Battery Charger Input Power

Problem detected with AC input power to the battery charger.

Check Battery Charger Output Power

Battery charger is not delivering expected output power for charging.

Battery Charger External/Environmental Fault

Battery charger failure caused by external or environmental factors.

Battery Charger Indicated Conditions

The battery charger has detected abnormal internal conditions requiring attention.

Generator Operational Limit Output Current

The generator has reached or exceeded its operating output current limit.

Failed J1939 CAN Comm Base Controller/Charger

J1939 CAN communication failure between the base controller and the battery charger.

Low Pressure Differential (Scroll only)

Low differential pressure detected across the compressor (Scroll only).

Battery Charger Fault – Unit Forced to Low Speed

The battery charger has a fault, and the unit is forced to low speed to protect the system.

Battery Charger Internal Short

An internal short circuit has been detected within the battery charger component.

Battery Charger External Short

A short circuit has been detected in the wiring or load external to the battery charger.

Battery Charger Output Voltage Exceeded Limit

The battery charger output voltage exceeded the maximum safety limit.

Battery Charger Operating Bulk Voltage Out of Range

The charging voltage during the 'Bulk' stage is outside the normal operating range.

Battery Charger Temperature Below Operating Range

The battery charger temperature is below the minimum operating range.

Battery Charger AC Input Overvoltage

AC input voltage to the battery charger exceeds the safe limit.

Battery Charger Internal Overvoltage Fault

Overvoltage fault detected within the battery charger internal circuits.

Battery Charger Internal Temp Sensor Fault

Fault in the sensor monitoring the internal temperature of the battery charger.

Battery Charger Charging – Low Battery

The charger detects an extremely low battery voltage during the charging cycle.

Check Exhaust Pressure Sensor

Fault in the exhaust pressure sensor, affecting emission control.

Check Intake Pressure Sensor

Fault in the Manifold Absolute Pressure (MAP) sensor.

Rail Pressure Fault

Fuel rail pressure is outside safe operating parameters.

High Temperature Alarm

Temperature above the configured limit.

High Discharge Pressure

High pressure switch opened due to overpressure.

Low Suction Pressure

Low pressure switch activated.

Compressor Thermal Protector Open

Protection module detected compressor overheating.

High Discharge Pressure (HP)

High pressure switch activated on Bitzer compressor.

Low Suction Pressure (LP)

Low pressure switch activated.

High Discharge Gas Temperature

PTC sensor in compressor head exceeded 140°C.

Oil Differential Pressure Failure

Delta P-MP10 detected low oil pressure for >90 seconds.

Battery Charger Operating Derated Due to High Temp

Battery charger has reduced its output current because internal temperature is too high.