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 Descriptor
DTC P0A8D: 14 Volt Power Module System Voltage LowDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Battery Positive Voltage | P0A8D* | P0AFF** | -- | -- |
* DTC while APM is charging. **DTC with APM prior to charging. | ||||
Circuit/System Description
The Accessory Power Module (APM) continuously monitors its 14 volt circuit during Normal mode and 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 Normal mode. |
| • | 14 volt circuit drops below 10.0 volts for 0.012 seconds during Jump Assist. |
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 14-volt conversions. |
Conditions for Clearing the DTC
| • | DTC P0A8D is a Type C DTC. |
| • | 14-volt circuit rises above 10.2 volts in Normal mode. |
| • | 14-volt circuit rises above 11.0 volts 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. |
| • | A poor ground connection between the APM chassis and vehicle ground may result in excess current passing through the 42-volt ground circuit connector X2 terminal 2 from the electric power steering circuit resulting in DTC P0A8D. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Drive Motor Generator Control Module Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Perform DC Power Conversion Test before performing Circuit/System Testing.
Circuit/System Testing
- Ignition OFF, disconnect the 14-volt and 42-volt harness connectors at the APM.
- Test for less than 1.0 ohm between the APM chassis and ground.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit connector X3 terminal 1 and ground.
- If all circuits test normal, replace the APM.
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
| ⇒ | If greater than the specified value, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for APM replacement, setup, and programming
