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DTC 50-52

DTC 50-52

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.


DTC Descriptors

DTC 50

Parking Heater Start Counter Overrun

DTC 51

Parking Heater Cold Blow Time Exceeded

DTC 52

Parking Heater Safety Time Exceeded

Circuit/System Description

The parking heater does not heat up instantly. It must go through a self test and start up procedure before normal operation. The parking heater depends on the fuel pump to deliver enough fuel in a timely manner. The electronic control module inside the heater determines when to turn on the fuel pump and the glow plug by monitoring coolant temperature and combustion temperature. The combustion sensor disables the glow plug once combustion is established and aborts the startup process if combustion is not established.

Conditions for Running the DTC

Ignition OFF. Battery voltage must be between 10-15 V.

Conditions for Setting the DTC

Before every start of the heater, the operation of the individual components is tested.

Action Taken When the DTC Sets

The parking heater will lock.

Conditions for Clearing the DTC

DTC must be cleared with the remote control.

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 Verification

Ignition OFF, command the independent heater ON and OFF with the remote control. Verify the independent heater turns ON and OFF with no DTCs.

Circuit/System Testing


1. Parking heater ON, verify DTC 12, 14 or 15 is not set.

2. If either DTC is set, refer to DTC 12, 14 or 15.

3. Check the G26 Parking Heater Fuel Pump and filter for constrictions or lack of fuel. Refer to Fuel Pump Test.

4. If the fuel filter is dirty, clean or replace the filter. Refer to Fuel Pump Filter Replacement.

5. Check exhaust and intake air manifolds for obstructions or improper location.

6. Check the B167 Parking Heater Combustion Sensor for values out of range. Refer to Combustion Sensor Test.

7. If everything tests normal, replace the K87 Parking Heater Control Module.


Component Testing


Fuel Pump Test

1. Ignition OFF, parking heater OFF, disconnect the fuel line at the K87 Parking Heater Control Module.

2. Turn the parking heater ON and ensure the fuel flows in an even, bubble-free stream.

3. Cycle the parking heater OFF and ON and record the amount of fuel that flows in 90 seconds. The fuel pump should flow 10.7-11.9 ccm in 90 seconds.

4. If not within the specified range, replace the G26 Parking Heater Fuel Pump.



Combustion Sensor Test

1. Ignition OFF, parking heater OFF, separate the K87 Parking Heater Control Module from the X150 Parking Heater Harness & Parking Heater Assembly Harness.

2. Test the B167 Parking Heater Combustion Sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Fuel Operated Heater Sensor Resistance Table .

3. If not within the specified range, replace the B167 Parking Heater Combustion Sensor.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.