For 1990-2009 cars only
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 Descriptor
DTC P279D: Four Wheel Drive (4WD) Range Signal CircuitCircuit/System Description
The hybrid powertrain control module (HPCM) monitors the state of the 4WD range signal message, if equipped, over the GMLAN communication bus. The HPCM uses this message to determine motor torque required and transmission shifting, there are no external circuits involved.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The HPCM has detected a 4WD range signal rolling count error for 8 seconds.
Action Taken When the DTC Sets
DTC P279D is a Type A DTC.
Conditions for Clearing the DTC
| • | DTC P279D is a Type A DTC. |
| • | When attempting to set HPCM internal DTCs, run the engine for at least 1 minute, and then shut the engine off for 30 seconds. Following this procedure will allow for a complete HPCM shutdown. Program the HPCM with the latest software version and retest the DTC to see if the DTC resets. |
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Verification
- Start the engine.
- Let the engine run for 1 minute, then turn the key OFF for 30 seconds.
- Retest for DTC P279D.
Circuit/System Testing
- Observe the 4WD Signal in the ECM Data List. The 4WD signal should display Enabled when you shift into 4WD and Disabled when you shift into 2WD.
- Program the HPCM with the latest software version and retest for DTCs.
| ⇒ | If the scan tool display does not match the transfer case range switch state, repair the transfer case system refer to Diagnostic Starting Point - Transfer Case. |
| ⇒ | If the scan tool matches the transfer case range switch state, continue with testing. |
| ⇒ | If the DTC resets, replace the HPCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for HPCM replacement, setup, and programming.
