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 P1A95: DC/DC Converter Stuck in 14-42 Volt Direction

DTC P1A96: DC/DC Converter Stuck in 42-14 Volt Direction

Circuit/System Description

The starter/generator control module (SGCM) monitors to detect auxiliary power module (APM) fault when the APM is commanded in the normal charge mode causing an over current condition. If a fault is detected, the appropriate DTC will set.

Conditions for Running the DTC

P1A95, P1A96

The engine is running.

Conditions for Setting the DTC

P1A95

DC-DC direction indicates 42-14 volt direction, but converter stays in 14-42 volt direction and current is greater than 20 amps for 1 second.

P1A96

DC-DC direction indicates 14-42 volt direction, but converter stays in 42-14 volt direction and current is less than -20 amps for 1 second.

Action Taken When the DTC Sets

P1A95, P1A96

    • Stop PWM (MGU shutdown)
    • APM PWM off
    • Battery disconnection (disconnect SW on/off)

Conditions for Clearing the DTC

P1A95, P1A96

Clears 30 seconds after cycle wakeup signal.

Diagnostic Aids

P1A95, P1A96

FET breakdown

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

Caution: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.

  1. With a scan tool, clear the DTC.
  2. Ignition OFF, wait 30 seconds.
  3. Ignition ON, operate the vehicle within the Conditions for Running the DTC.
  4. 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