P0A8D

DTC P0A8D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (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 P0A8D
- 14 Volt Power Module System Voltage Low

Diagnostic Fault Information





Circuit/System Description

The Accessory Power Module (APM) continuously monitors its 14V circuit during Normal mode and Jump Assist. This DTC sets when the 14V circuit in the APM drops below a set level. APM functions will run only when an APM enable message from the Hybrid powertrain control module (HPCM) is active on the high speed hybrid GMLAN communication circuit.

Conditions for Running the DTC

APM 14V enable message active.

Conditions for Setting the DTC

14V circuit drops below 10.0V during Normal or Jump Assist mode.

Action Taken When the DTC Sets

* DTC P0A8D is a Type C DTC.
* The engine control module (ECM) will command the charge indicator and or warning message to be illuminated on the instrument panel cluster (IPC) and the driver information center (DIC), if equipped.
* The ECM will not illuminate the malfunction indicator lamp (MIL).
* The HPCM stores the DTC information in memory when the diagnostic runs and fails.
* The APM will shutdown 14V conversions.

Conditions for Clearing the DTC

* DTC P0A8D is a Type C DTC.
* 14V circuit rises above 10.2V in Normal mode.
* 14V circuit rises above 11.0V during Jump Assist.

Diagnostic Aids

A charging system malfunction may cause variances in system voltage and set voltage related DTCs. Refer to DC Power Conversion Test (Hybrid Controls - HP5).

Reference Information
Schematic Reference

Hybrid Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Drive Motor Generator Control Module Description and Operation (Description and Operation)
Electrical Information Reference

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

Perform DC Power Conversion Test (Hybrid Controls - HP5) before performing Circuit/System Testing.

Circuit/System Testing

Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the 14V harness connector at the APM.
2. Test for less than 1.0 ohm between the APM chassis and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit connector X3 terminal A and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the APM.

Repair Instructions

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

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