GM Service Manual Online
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 Descriptors

DTC P1A63: Starter/Generator Control Module Internal Circuit

DTC P1A69: Starter/Generator Control Module Random Access Memory (RAM)

DTC P1A6A: Starter/Generator Control Module Read Only Memory (ROM)

DTC P1A6B: Starter/Generator Control Module 5 Volt Reference Circuit

Circuit/System Description

The starter/generator control module (SGCM) monitors to detect internal faults. If a fault is detected, the appropriate DTC will set.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P1A63

The gate driver voltage fault signal is low or PWM logic error fault signal is low.

P1A69

RAM check error

P1A6A

RAM check error (calculated ROMSUM value does not match with defined value).

P1A6B

5 volt reference fault, 5 volt input AD value (2 byte) is out of the range for 100 ms.

Action Taken When the DTC Sets

P1A63, P1A69, P1A6A, P1A6B

    • Stop PWM (MGU shutdown)
    • APM PWM Off

Conditions for Clearing the DTC

P1A63, P1A69, P1A6A, P1A6B

Clears 30 seconds after cycle wake up signal.

Diagnostic Aids

P1A63, P1A69, P1A6A, P1A6B

Possible internal electrical failure of the SGCM.

Reference Information

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Starter/Generator Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, verify that the latest service software is installed.
  2. With a scan tool, clear the DTC.
  3. Ignition OFF, wait 30 seconds.
  4. Ignition ON, operate the vehicle within the Conditions for Running the DTC and verify the DTC does not reset.
  5. If the DTC resets, replace the SGCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for SGCM replacement, setup, and programming