P279D

DTC P279D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptor
DTC P279D
- Four Wheel Drive (4WD) Range Signal Circuit

Circuit/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 (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information.

Circuit/System Verification

1. Start the engine.
2. Let the engine run for 1 minute, then turn the key OFF for 30 seconds.
3. Retest for DTC P279D.

Circuit/System Testing

1. 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.

• 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 (BW 4485-NR3 - Transfer Case) for BW 4485-NR3 or Diagnostic Starting Point - Transfer Case (MP 3023/3024-NQH - Transfer Case) for MP 3023/3024-NQH.

• If the scan tool matches the transfer case range switch state, continue with testing.

2. Program the HPCM with the latest software version and retest for DTCs.

• If the DTC resets, replace the HPCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for HPCM replacement, setup, and programming.