GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Malibu 🢒 Hybrid 🢒 Hybrid Controls 🢒 DTC P1A8D or P1A8E

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 P1A8D: 14 Volt Power Module Voltage Sensor Circuit Low Voltage

DTC P1A8E: 14 Volt Power Module Voltage Sensor Circuit High Voltage

Circuit/System Description

The auxiliary power module (APM) 12-volt output voltage is used for a 12-volt line APM output voltage control and a 12-volt line voltage sensor rationality check. The starter/generator control module (SGCM) monitors the voltage sensor for the following:

    • To detect the failure of the APM 12-volt voltage sensor circuit below valid range.
    • To detect the failure of the APM 12-volt voltage sensor circuit above valid range.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P1A8D

Sensor output voltage less than 0.5 volt for 0.5 ms and the 12-volt power supply - 12-volt output voltage is greater than 5 volts for 0.5 ms.

P1A8E

Sensor output voltage greater than 4.2 volts (30.2 volts) for 0.5 ms and the 12-volt power supply - 12-volt output voltage is greater than 5 volts for 0.5 ms.

Action Taken When the DTC Sets

P1A8D, P1A8E

    • Stop PWM (MGU shutdown).
    • APM PWM off.

Conditions for Clearing the DTC

P1A8D, P1A8E

Clears 30 seconds after cycle wake up signal.

Diagnostic Aids

P1A8D

Possible internal sensor short to ground or open.

P1A8E

Possible internal sensor short to voltage or open.

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

P1A8D, P1A8E

  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