Transport Refrigeration Unit (Reefer) Fault Codes
The diesel-powered "reefer unit" mounted on the nose of a refrigerated trailer or straight truck -- Thermo King and Carrier Transicold are the two manufacturers that dominate the road. Owner-operators and refrigerated-fleet mechanics (including mobile repair trucks running agricultural corridors like California's Central Valley) hit these alarm codes constantly, and documentation is notoriously scattered across dealer PDFs and forum posts. This hub covers the alarm meanings, real causes, and diagnostic steps in plain language.
41 fault codes documented· 2 brands (Thermo King, Carrier Transicold) · Trailer / straight-truck reefer units
Most Common Reefer Unit Fault Codes
Showing 30 of 41 Transport Refrigeration codes across Thermo King and Carrier Transicold, sorted by severity. Each links to causes, diagnostics, and common fixes.
CARRIER-TRANSICOLD-00013 critical
High Compressor Discharge Pressure Shutdown
CARRIER-TRANSICOLD-00017 critical
High Compressor Discharge Temperature Shutdown
CARRIER-TRANSICOLD-00018 critical
Low Suction Pressure Shutdown Alarm
CARRIER-TRANSICOLD-00028 critical
Check Refrigeration System Low Delta Fault
CARRIER-TRANSICOLD-00056 critical
Evaporator Airflow Restricted or Fan Fault Detected
CARRIER-TRANSICOLD-00075 critical
Compressor Motor Overload Protector Tripped
CARRIER-TRANSICOLD-00076 critical
Condenser Fan Motor Overload Protector Tripped
CARRIER-TRANSICOLD-00077 critical
Evaporator Fan Motor Overload Protector Tripped
CARRIER-TRANSICOLD-00100 critical
Overload Or Ground Fault Detected On Electrical System
CARRIER-TRANSICOLD-00246 critical
EPROM Write Failure: Non-Volatile Memory Save Error
CARRIER-TRANSICOLD-00249 critical
APX Microprocessor Internal Control Board Fault
CARRIER-TRANSICOLD-00255 critical
APX Controller System Failure Detected
THERMO-KING-10 critical
High Discharge Pressure Compressor Shutdown
THERMO-KING-12 critical
Sensor or Digital Input Shutdown Zone
THERMO-KING-17 critical
Engine Failed to Crank on Start Attempt
THERMO-KING-18 critical
High Engine Coolant Temperature Shutdown
THERMO-KING-19 critical
Low Engine Oil Pressure Shutdown
THERMO-KING-23 critical
Cooling Cycle Fault Zone Failed to Complete
THERMO-KING-32 critical
Refrigeration Capacity Low, Zone Locked Out
THERMO-KING-509 critical
ECU Failed to Enable Engine Start Command
THERMO-KING-516 critical
I/O Controller to Application Controller Communication Failure
THERMO-KING-616 critical
Engine Overspeed Shutdown Detected
THERMO-KING-82 critical
High Compressor Discharge Temperature Shutdown
CARRIER-TRANSICOLD-00030 serious
Unit Failed to Complete Minimum Run Time
THERMO-KING-09 serious
High Evaporator Temperature Detected in Cargo Zone
THERMO-KING-505 serious
Roadside Condenser Fan Motor Speed Circuit Fault
THERMO-KING-519 serious
Battery Charger Input Power Fault Detected
THERMO-KING-61 serious
Low Battery Voltage Detected on Control Circuit
THERMO-KING-615 serious
Common-Rail Fuel Pressure Out of Range
THERMO-KING-66 serious
Low Engine Oil Level Detected
Reefer Unit Brands
| Brand | Applications | Notes |
|---|---|---|
| Thermo King | Precedent S-600 / S-700 / S-800 (trailer), Precedent C-600 / C-800 (straight truck) | Smart Reefer 4 (SR-4) touchscreen/hard-key control panel. Alarms show as 2-3 digit numbers under the Alarm Menu -- 00-99 general codes, 500-series Precedent refrigeration/electrical, 600 and 800-series Precedent engine codes. |
| Carrier Transicold | Vector 6100 / 6500 / 8100 / 8500 (multi-temp trailer), Supra and Ultra (older trailer lines) | APX / Advance / Aspen microprocessor control system, Display Module (DM) keypad/LCD. Alarms show as 5-digit numbers (e.g. 00013), scrolled via the MENU key. Color-coded severity: Red = shutdown, Yellow = caution. |
Common Reefer Unit Issues
- High discharge pressure (Thermo King 10, Carrier 00013/00017) -- dirty or blocked condenser coil is the most common cause
- Low oil pressure engine shutdown (Thermo King 19) -- check oil level first, the #1 cause of this code
- Engine won't crank / no cooling at all (Thermo King 17, engine ECU faults) -- starting circuit or engine fault, unit produces zero refrigeration
- Sensor circuit faults (Carrier 00121-00124) -- ambient, return, supply, or defrost-termination sensor wiring, usually a caution-level alarm, not a shutdown
- Motor overload trips (Carrier 00075/00076/00077) -- compressor, condenser fan, or evaporator fan motor drawing excess current
- Low fuel / low battery (Thermo King 96 / 61) -- routine warnings that become urgent if ignored mid-route
- Box temperature out of range (Carrier 00053) -- load, door seal, or airflow issue threatening cold-chain compliance