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Fuel Operated Heater Malfunction

Fuel Operated Heater Malfunction

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


Circuit/System Description

The parking heater work independently of the engine and thus offer a double plus: preheating the vehicle passenger compartment and the engine. The parking heater is integrated in the water cooling system of the engine. The thermal energy gained is absorbed by the vehicles own heat exchanger and distributed into the interior through their existing air vents. The engine is warmed up with the residual heat in the water cooling system of the engine.

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel Operated Heater Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Circuit/System Testing


1. Check the fuel operated heater DTCs, refer to Fuel Operated Heater Diagnostic Trouble Code (DTC) Displaying and Clearing .

2. Check fuel operated heater remote control. For fuel operated heater remote control malfunction refer to Fuel Operated Heater Diagnostic Trouble Code (DTC) Displaying and Clearing .

3. Ignition OFF, disconnect the harness connector at the K87B Parking Heater Control Module - Auxiliary.

4. Test for less than 5 Ω between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 25 and ground.

5. If greater than the specified range, test the ground circuit for an open/high resistance.

6. Connect the harness connector at the K87B Parking Heater Control Module - Auxiliary.

7. Turn ON the parking heater with the radio remote control, confirm operating time. Check if the blower motor begin to run after about 5 minutes.

8. If the blower motor did not run, turn OFF the parking heater.

9. Disconnect the harness connector at the K87B Parking Heater Control Module - Auxiliary.

10. Test for less than 5 Ω between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 18 and X84 Data Link Connector terminal 1.

11. If the value is greater than the specified value, test the serial data circuit for an open circuit/high resistance. If the circuit test normal, replace the K87B Parking Heater Control Module - Auxiliary.

12. Test for more than 11 V at the K87B Parking Heater Control Module - Auxiliary harness connector terminal 4, 8, 26 and ground.

13. If less than the specified value, test the B+ (battery positive voltage) circuit for an open/high resistance.

14. Disconnect the harness connector at the K88 Parking Heater Remote Control Receiver and K87 Parking Heater Control Module.

15. Ignition ON, test for less than 0.3 V between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 3 and ground.

16. If greater than the specified value, test the control circuit for a short to voltage.

17. Ignition OFF, test for more than 500 kΩ between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 3 and ground.

18. If greater than the specified value, test the control circuit for a short to ground.

19. Test for less than 5 Ω between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 3 and K87B Parking Heater Control Module - Auxiliary harness connector terminal 21.

20. If greater than the specified value, test the control circuit for an open/high resistance.

21. Test for less than 5 Ω between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 3 and K88 Parking Heater Remote Control Receiver harness connector terminal 10.

22. If greater than the specified value, test the control circuit for an open/high resistance.

23. Test for less than 5 Ω between the K87B Parking Heater Control Module - Auxiliary harness connector terminal 3 and K87 Parking Heater Control Module harness connector terminal 5.

24. If greater than the specified value, test the control circuit for an open/high resistance.

25. Connect the harness connector at the components listed below:

• K87B Parking Heater Control Module - Auxiliary

• K87 Parking Heater Control Module

• K88 Parking Heater Remote Control Receiver

26. Remove the KR106 Parking Heater Relay.

27. Connect a test lamp between the KR106 Parking Heater Relay control circuit terminal 3 and terminal 5.

28. Turn the parking heater ON/OFF with the radio remote control, confirm operating time. The test lamp should turn ON/OFF when changing between the commanded states.

29. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K87B Parking Heater Control Module - Auxiliary.

30. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K87B Parking Heater Control Module - Auxiliary.

31. If all circuits test normal, replace the K87B Parking Heater Control Module - Auxiliary or the K87 Parking Heater Control Module.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.