What does Thermo King alarm code 00 mean?

No Alarms Exist. Operator action: No action required.

What does Thermo King alarm code 02 mean?

Check Evaporator Coil Sensor (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 03 mean?

Check (Control); Return Air Sensor (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 04 mean?

Check (Control); Discharge Air Sensor (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 05 mean?

Check Ambient Temp Sensor. Operator action: Report alarm at end of day.

What does Thermo King alarm code 06 mean?

Check Coolant Temp Sensor. Operator action: Report alarm at end of day.

What does Thermo King alarm code 07 mean?

Check Engine RPM Sensor. Operator action: Report alarm at end of day.

What does Thermo King alarm code 08 mean?

Unit Running on Coil Sensor (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code (09) mean?

High Evaporator Temperature (Zone). Operator action: If unit/zone is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (10) mean?

High Discharge Pressure (or Temperature). Operator action: If unit is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code 11 mean?

Unit or Zone Controlling on Alternate Sensor (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 12 mean?

Sensor or Digital Input Shutdown (Zone). Operator action: Unit/zone cannot operate and is shut down. Repair immediately.

What does Thermo King alarm code 13 mean?

Sensor Check (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 14 mean?

Defrost Terminated by Time. Operator action: Report alarm at end of day.

What does Thermo King alarm code 15 mean?

Check Glow Plugs or Intake Air Heater. Operator action: If unit is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code 16 mean?

Manual Start Not Completed. Operator action: Report alarm at end of day.

What does Thermo King alarm code (17) mean?

Engine Failed to Crank. Operator action: If unit is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (18) mean?

High Engine Coolant Temperature. Operator action: If unit is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (19) mean?

Low Engine Oil Pressure. Operator action: If unit is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (20) mean?

Engine (Vapor Motor CR) Failed to Start. Operator action: If unit/zone is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (21) mean?

Cooling Cycle Check (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code (22) mean?

Heating Cycle Check (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 23 mean?

Cooling Cycle Fault (Zone). Operator action: Unit/zone cannot operate and is shut down. Repair immediately.

What does Thermo King alarm code 24 mean?

Heating Cycle Fault (Zone). Operator action: Unit/zone cannot operate and is shut down. Repair immediately.

What does Thermo King alarm code 25 mean?

Alternator Check. Operator action: If unit/zone is shut down repair immediately. Otherwise, report alarm at end of day.

What does Thermo King alarm code (26) mean?

Check Refrigeration Capacity (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code (27) mean?

Vapor Motor RPM High (CR). Operator action: Unit cannot operate and is shut down. Repair immediately.

What does Thermo King alarm code 28 mean?

Pretrip or Self Check Abort. Operator action: Report alarm at end of day.

What does Thermo King alarm code 29 mean?

Defrost Damper Circuit Check (Zone). Operator action: Manually monitor temperature. Report alarm at end of day.

What does Thermo King alarm code 30 mean?

Defrost Damper Stuck Closed (Zone). Operator action: Unit/zone cannot operate and is shut down. Repair immediately.

Thermo King Alarm Codes & Fault Codes — Complete List (00–899) | Peak Thermo King

🔧 Official Reference Guide

Thermo King Alarm Codes & Fault Codes

The complete reference for all Thermo King truck, trailer, CR, DAS & DSR alarm codes — with status levels and operator actions for every code.

288Total Alarm Codes

3Severity Levels

12Service Locations

Truck Units Trailer Units CR Units DAS Units DSR Units TriPac Precedent Series

Whether you're seeing a red shutdown alarm, a yellow check code, or just a green status notice, this guide covers every Thermo King fault code from Code 00 through Code 899 — including DSR alpha codes like LP, HP, OL, SOF, tEP, and more.

📍 Find Your Nearest Location

OK to Run Check as Specified Immediate Action

⚠️ Note: Codes in parentheses (XX) may appear alongside alarm code 84 and may clear automatically. On multi-temp units, the zone will be identified. Record all alarms to assist your technician.

00 No Alarms Exist OK to Run ▼

02 Check Evaporator Coil Sensor (Zone) Check ▼

03 Check (Control); Return Air Sensor (Zone) Check ▼

04 Check (Control); Discharge Air Sensor (Zone) Check ▼

05 Check Ambient Temp Sensor OK to Run ▼

06 Check Coolant Temp Sensor OK to Run ▼

07 Check Engine RPM Sensor OK to Run ▼

08 Unit Running on Coil Sensor (Zone) Check ▼

(09) High Evaporator Temperature (Zone) Check ▼

(10) High Discharge Pressure (or Temperature) Immediate Action ▼

11 Unit or Zone Controlling on Alternate Sensor (Zone) Check ▼

12 Sensor or Digital Input Shutdown (Zone) Immediate Action ▼

13 Sensor Check (Zone) Check ▼

14 Defrost Terminated by Time OK to Run ▼

15 Check Glow Plugs or Intake Air Heater Check ▼

16 Manual Start Not Completed OK to Run ▼

(17) Engine Failed to Crank Check ▼

(18) High Engine Coolant Temperature Check ▼

(19) Low Engine Oil Pressure Check ▼

(20) Engine (Vapor Motor CR) Failed to Start Check ▼

(21) Cooling Cycle Check (Zone) Check ▼

(22) Heating Cycle Check (Zone) Check ▼

23 Cooling Cycle Fault (Zone) Immediate Action ▼

24 Heating Cycle Fault (Zone) Immediate Action ▼

25 Alternator Check Check ▼

(26) Check Refrigeration Capacity (Zone) Check ▼

(27) Vapor Motor RPM High (CR) Immediate Action ▼

28 Pretrip or Self Check Abort OK to Run ▼

29 Defrost Damper Circuit Check (Zone) Check ▼

30 Defrost Damper Stuck Closed (Zone) Immediate Action ▼

31 Check Oil Pressure Switch Check ▼

32 Refrigeration Capacity Low (Zone) Immediate Action ▼

33 Check Engine RPM OK to Run ▼

34 Check Modulation Circuit Check ▼

35 Check Run Relay Circuit Immediate Action ▼

(36) Electric Motor Failed to Run Immediate Action ▼

37 Check Engine Coolant Level OK to Run ▼

38 Electric Phase Reversed Immediate Action ▼

39 Check Water Valve Circuit Check ▼

40 Check High Speed Circuit Check ▼

41 Check Engine Coolant Temp Check ▼

42 Unit Forced to Low Speed Check ▼

43 Unit Forced to Low Speed Modulation OK to Run ▼

44 Check Fuel System Immediate Action ▼

45 Check Hot Gas or Hot Gas Bypass Circuit Check ▼

46 Check Air Flow (Zone) Check ▼

47 Remote Sensor Shutdown Immediate Action ▼

48 Check Belts or Clutch Immediate Action ▼

49 Check Spare Sensor 1 OK to Run ▼

50 Reset Clock OK to Run ▼

51 Check Shutdown Circuit Immediate Action ▼

52 Check Heat Circuit (Zone) Check ▼

53 Check Economizer Valve Circuit Check ▼

54 Test Mode Timeout OK to Run ▼

55 Check Engine Speeds OK to Run ▼

56 Check Evaporator Fan Low Speed (Zone) Check ▼

57 Check Evaporator Fan High Speed (Zone) Check ▼

61 Low Battery Voltage Check ▼

62 Ammeter Out of Calibration Immediate Action ▼

(63) Engine or Vapor Motor Stopped Immediate Action ▼

64 Pretrip Reminder OK to Run ▼

65 Abnormal Temperature Differential (Zone) Check ▼

66 Low Engine Oil Level Immediate Action ▼

67 Check Liquid Line Solenoid Circuit (Zone) Check ▼

68 Internal Controller Fault Code Immediate Action ▼

70 Hourmeter Failure OK to Run ▼

71 Hourmeter 4 Exceeds Set Time Limit OK to Run ▼

72 Hourmeter 5 Exceeds Set Time Limit OK to Run ▼

73 Hourmeter 6 Exceeds Set Time Limit OK to Run ▼

74 Controller Reset to Defaults OK to Run ▼

75 Controller RAM Failure Immediate Action ▼

76 Controller EPROM Failure Immediate Action ▼

77 Controller EPROM Checksum Failure Immediate Action ▼

78 Data Log EPROM Failure Immediate Action ▼

79 Internal Data Logger Overflow OK to Run ▼

80 Check Compressor Temp Sensor OK to Run ▼

81 High Compressor Temp Immediate Action ▼

82 High Compressor Temp Shutdown Immediate Action ▼

83 Low Engine Coolant Temp OK to Run ▼

84 Restart Null OK to Run ▼

85 Forced Unit Operation OK to Run ▼

86 Check Discharge Pressure Sensor OK to Run ▼

87 Check Suction Pressure Sensor OK to Run ▼

88 Reserved for CR OK to Run ▼

89 Check Electronic Throttling Valve (ETV) Circuit OK to Run ▼

90 Electric Overload OK to Run ▼

91 Check Electric Ready Input OK to Run ▼

92 Sensor Grades Not Set (Zone) OK to Run ▼

93 Low Compressor Suction Pressure OK to Run ▼

94 Check Loader #1 Circuit OK to Run ▼

95 Check Loader #2 Circuit OK to Run ▼

96 Low Fuel Level Check ▼

97 Failed Remote Return Air Sensor (CR) Immediate Action ▼

98 Check Fuel Level Sensor OK to Run ▼

99 High Compressor Pressure Ratio Immediate Action ▼

(100) Heater Fan Failure (CR) Check ▼

101 Controlling on Evap Coil Outlet Temp (CR) Immediate Action ▼

(102) Low Evaporator Coil Temperature (CR) Check ▼

103 Low Heater Fuel Level (CR) Check ▼

104 Check Remote Fan Speed (Zone) Check ▼

105 Check Receiver Tank Press Sol Circuit Check ▼

106 Check Purge Valve Circuit Check ▼

107 Check Condenser Inlet Sol Circuit Check ▼

108 Door Open Timeout (Zone) Check ▼

110 Check Suction Line Sol Circuit (Zone) Check ▼

111 Unit Not Configured Correctly (Zone) OK to Run ▼

112 Check Remote Fans (Zone) Check ▼

113 Check Electric Heat Circuit (Zone) Check ▼

114 Multiple Alarms – Cannot Run (Zone) Immediate Action ▼

115 Check High Pressure Cut Out Switch Check ▼

116 Check High Pressure Cut In Switch OK to Run ▼

117 Auto Switch from Diesel to Electric OK to Run ▼

118 Auto Switch from Electric to Diesel OK to Run ▼

120 Check Alternator Excite Circuit Check ▼

121 Check PMW Liquid Injection Circuit Check ▼

122 Check Diesel/Electric Circuit Check ▼

123 Check Evap Coil Inlet Temp Sensor (CR) Check ▼

124 Check Evap Coil Outlet Temp Sensor (CR) OK to Run ▼

125 Check Tank Level Sensor (CR) Check ▼

126 Check Back Pressure Regulator (CR) Check ▼

127 Setpoint Not Entered (Zone) Check ▼

128 Engine Run Time Maint Reminder #1 / Service Due OK to Run ▼

129 Engine Run Time Maint Reminder #2 OK to Run ▼

130 Engine Run Time Maint Reminder #1 OK to Run ▼

131 Electric Run Time Maint Reminder #2 OK to Run ▼

132 Total Unit Run Time Maint Reminder #1 OK to Run ▼

133 Total Unit Run Time Maint Reminder #2 OK to Run ▼

134 Controller Power On Hours OK to Run ▼

135 Check Spare Digital Inputs OK to Run ▼

137 Check Spare Digital Outputs OK to Run ▼

137* Check Damper Motor Heater Output Check ▼

138 Log DAS Real Time Clock Battery Failure (DAS) OK to Run ▼

139 Abort Evacuation Mode OK to Run ▼

141 Auto Switch Diesel to Electric Disabled Check ▼

142 Check Thermax Valve Check ▼

143 Check Remote Drain Hose Heater Output (Zone) OK to Run ▼

144 Lost CAN Communications to Expansion Module Immediate Action ▼

145 Lost Controller ON Feedback Signal Check ▼

146 Software Version Mismatch OK to Run ▼

147 Check Multi-Temp Fan Speed Control Output (Zone) Check ▼

148 Auto Switch Electric to Diesel Disabled Check ▼

149 Alarm Not Identified Check ▼

150 Sensor Out of Range Low (DAS and HMI) (Zone) OK to Run ▼

151 Sensor Out of Range High (DAS and HMI) (Zone) OK to Run ▼

152 DAS Failed Sensor (DAS) OK to Run ▼

153 Expansion Module Flash Load Failure OK to Run ▼

154 Low Suction Pressure Switch Failure Check ▼

155 Lost CAN Communications to HMI Immediate Action ▼

156 Check Suction/Liquid Heat Exchanger Bypass Valve Check ▼

157 OptiSet Plus Profile Mismatch OK to Run ▼

158 Primary Software Failed to Load OK to Run ▼

159 Check Battery Condition OK to Run ▼

160 Lost CAN Communications to Radio Expansion Board OK to Run ▼

161 Log DAS Real Time Clock Invalid (DAS) OK to Run ▼

163 Emission Control Failure Check ▼

175 Check Electronic Expansion Valve (CR) Check ▼

176 Check Evaporator Pressure Sensor (CR) Check ▼

177 Check CO2 Tank Pressure Sensor (CR) Check ▼

178 Low CO2 Fuel Level (CR) Check ▼

180 TriPac Compressor Alarm Check ▼

188 Log DAS Microprocessor Fault (DAS) Check ▼

203 Check Display Return Air Sensor (Zone) Check ▼

204 Check Display Discharge Air Sensor (Zone) Check ▼

216 Check DAS Digital Inputs (DAS) OK to Run ▼

233 REB Switching Off, Conservative to Full Null OK to Run ▼

234 Check Relative Humidity Sensor Circuit OK to Run ▼

235 High Engine Coolant Temperature Check OK to Run ▼

250 DAS Clock Time Reset (DAS) OK to Run ▼

251 Check Radio Expansion Board Configuration OK to Run ▼

252 Check Auto Fresh Air Exchange Circuit OK to Run ▼

253 REB On Back Up Battery, Alarms Disabled OK to Run ▼

254 Check Auxiliary Coolant Temp Sensor OK to Run ▼

500 Check Host Evaporator Blower Low Speed Check ▼

501 Check Host Evaporator Blower High Speed Check ▼

505 Check Roadside Condenser Fan Motor Speed Circuit Check ▼

506 Check Curbside Condenser Fan Motor Speed Circuit Check ▼

507 Check Digital Scroll Output Circuit (Scroll Only) OK to Run ▼

508 Speed Request Communication Error OK to Run ▼

509 ECU Failed to Enable Check ▼

510 ECU Run Signal Failed Check ▼

511 Engine Wait to Start Time Delay Expired OK to Run ▼

512 High Compressor Suction Pressure (Scroll Only) Check ▼

513 Low Compressor Suction Ratio (Scroll Only) Check ▼

514 Low Compressor Discharge Pressure (Scroll Only) Check ▼

515 Minimum ETV Discharge Superheat Temp (Scroll) Check ▼

516 I/O Controller to Application Controller Com Failure Immediate Action ▼

518 Generator Ground Fault Check ▼

519 Check Battery Charger Input Power Check ▼

520 Check Battery Charger Output Power Check ▼

521 Battery Charger External/Environmental Fault Check ▼

522 Battery Temperature Sensor Alarm Check ▼

523 Battery Charger Indicated Conditions Check ▼

524 Generator Op Limit Vout to Frequency Ratio Check ▼

525 Generator Frequency Range Fault Check ▼

526 Generator Operational Limit Output Current Check ▼

528 Failed J1939 CAN Comm Base Controller/Charger Check ▼

529 Check Fuel Pump Circuit Check ▼

530 Low Pressure Differential (Scroll only) Check ▼

531 Check Economizer Pressure Sensor (Scroll only) Check ▼

538 Engine J1939 CAN Data Link Degraded Check ▼

539 Engine J1939 CAN Data Link Failed Check ▼

540 Illegal Engine Operating State Check ▼

542 Battery Charger Fault – Unit Forced to Low Speed OK to Run ▼

543 Battery Charger Internal Short OK to Run ▼

544 Battery Charger External Short OK to Run ▼

545 Battery Charger Output Voltage Exceeded Limit OK to Run ▼

546 Battery Charger Operating Bulk Voltage Out of Range OK to Run ▼

547 AC Bus Phase Loss Check ▼

548 Battery Charger Temperature Below Operating Range OK to Run ▼

549 Battery Charger AC Input Overvoltage OK to Run ▼

550 Battery Charger Internal Overvoltage Fault Check ▼

551 Battery Charger Internal Temp Sensor Fault OK to Run ▼

552 Battery Charger Charging – Low Battery OK to Run ▼

553 Battery Charger Operating Derated Due to High Temp OK to Run ▼

599 Engine Service Tool Connected OK to Run ▼

600 Check Crankshaft Speed Sensor OK to Run ▼

601 Check Camshaft Speed Sensor OK to Run ▼

603 Check Exhaust Pressure Sensor OK to Run ▼

604 Check Coolant Temp Sensor (ECU) OK to Run ▼

605 Check Fresh Air Temp Sensor OK to Run ▼

607 Check Fuel Temperature Sensor OK to Run ▼

608 Check Rail Pressure Sensor OK to Run ▼

609 Check Intake Pressure Sensor OK to Run ▼

610 Check Atmospheric Pressure Sensor OK to Run ▼

611 Check Glow Plug Circuit (ECU) OK to Run ▼

613 Check Injectors OK to Run ▼

614 Check High Pressure Fuel Pump OK to Run ▼

615 Rail Pressure Fault Check ▼

616 Engine Overspeed Check ▼

617 Internal ECU Fault Check ▼

618 Check EGR System OK to Run ▼

619 ECU Main Relay Fault OK to Run ▼

620 No RPM Detected During Start Attempt Check ▼

623 TRUCAN Message Timeout OK to Run ▼

624 Check EGR Temperature Sensor OK to Run ▼

625 Check Intake Air Temperature Sensor OK to Run ▼

626 Check Exhaust Temperature Sensor OK to Run ▼

642 ECU Forced Low Speed OK to Run ▼

699 Unknown ECU Fault Check ▼

800 Crankshaft Position Sensor Error OK to Run ▼

801 Camshaft Position Sensor Error OK to Run ▼

804 Engine Coolant Temperature Sensor Error OK to Run ▼

807 Fuel Temperature Sensor Error OK to Run ▼

808 Rail Pressure Sensor Error OK to Run ▼

809 Intake Air Pressure Sensor Error OK to Run ▼

810 Atmospheric Pressure Sensor Error OK to Run ▼

811 Glow Plug Circuit Error OK to Run ▼

813 General Injector Error OK to Run ▼

815 Fuel Pressure Regulator Error Check ▼

818 EGR Valve Actuator Error OK to Run ▼

819 ECU Power Relay Error OK to Run ▼

825 T1 Air Intake Temperature Sensor Error OK to Run ▼

826 T2 Air Intake Temperature Sensor Error OK to Run ▼

827 EGR Valve Position Sensor Error OK to Run ▼

828 Lambda System Error OK to Run ▼

829 Main ECU Relay Error / Engine Communication Error OK to Run ▼

830 Air Flow Meter Error OK to Run ▼

832 Engine Power Supply Error OK to Run ▼

833 High Pressure Pump Fuel Metering Unit Error OK to Run ▼

834 Water in Fuel Sensor Error OK to Run ▼

836 Major ECU Failures OK to Run ▼

838 Intake Air System Error OK to Run ▼

839 Engine Speed Error OK to Run ▼

840 Fuel Injection Energizing Error OK to Run ▼

841 High Pressure Pump Wear OK to Run ▼

842 Engine Running in Safe Mode – Low Speed OK to Run ▼

843 Fuel Injection System Error OK to Run ▼

844 Engine Failed to Crank (ECU) OK to Run ▼

845 Starter Relay Error OK to Run ▼

846 T50 Switch Error OK to Run ▼

847 Variant Coding Error OK to Run ▼

853 Engine Overspeed (No DTC) Check ▼

854 Engine Protection Self Shutdown Check ▼

899 Unknown ECU Fault Check ▼

SOF Microprocessor Software Failure Immediate Action ▼

tEP Electric Standby Motor Thermal Protection Alarm Immediate Action ▼

- C - Communications Failure, Microprocessor to In-Cab Control Box Immediate Action ▼

dr2 Door 2 Open / Door Switch 2 Failure Check ▼

LP Low Suction Pressure Immediate Action ▼

P1E Return Air Temperature Sensor Fault Check ▼

HP High Discharge Pressure Immediate Action ▼

dr1 Door 1 Open / Door Switch 1 Failure Check ▼

OL Electric Standby Overload Immediate Action ▼

P2E Remote Return Air Temperature Sensor Fault Check ▼

bAt Low Battery Voltage (DSR) Immediate Action ▼

tP4 Power Supply Thermal Protection Alarm Immediate Action ▼

PSE High Pressure Sensor Fault Immediate Action ▼

tCO Electronic Control Module Internal Temperature Exceeds Limit Immediate Action ▼

🚨 Need Service? 12 Locations Ready to Help.

Seeing a red alarm or unit shut down? Our factory-trained Thermo King technicians are standing by across Texas, the Pacific Northwest, and the Mountain West.

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