P0A8D

DTC P0A8D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 14 volt circuit during charge or Jump Assist. This DTC sets when the 14 volt 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 14 volt enable message active.

Conditions for Setting the DTC

* 14 volt circuit drops below 10.0 volts for 0.03 seconds during charge.
* 14 volt circuit drops below 10.0 volts for 0.012 seconds during Jump-Assist.

Action Taken When the DTC Sets

* 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 14 volt conversions.

Conditions for Clearing the DTC

14 volt circuit rises above 10.2 volts.

Diagnostic Aids

DTC P0A8F will also be set as a result of this DTC setting in the APM. Diagnose DTC P0A8D before attempting to diagnose DTC P0A8F.

A charging system malfunction may cause variances in system voltage and set voltage related DTCs. Refer to DC Power Conversion Test.

A poor ground connection between the APM chassis and vehicle ground may result in excess current passing through the 42 volt ground circuit terminal [X] from the electric power steering circuit resulting in DTC P0A8D.

Circuit/System Verification

Perform DC Power Conversion Test before performing Circuit/System Testing.

Circuit/System Testing

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

1. Ignition OFF, disconnect the 14 volt and 42 volt harness connectors at the APM.
2. Test for less than 5.0 ohm of resistance 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 terminal [X] 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 after completing the diagnostic procedure. Verification Tests