PRE-RELEASE
DTC 91
| DTC 91 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| DTC Descriptor |
DTC 91
Parking Heater External Interference Voltage
| 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.
| Diagnostic Aids |
Ensure that all power related DTCs are diagnosed and corrected prior to diagnosing this DTC.
| 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
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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| 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. |
Attempt to clear the DTC with the remote control.
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| 2. |
Ensure that there are no high amperage circuits near the parking heater circuits.
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| 3. |
If all circuits test normal and the DTC will not clear, replace the K87 Parking Heater Control Module.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
