P1A8E

DTC P1A8D or P1A8E

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 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 sensor short to ground or open.

P1A8E

Possible short to voltage or open.

Circuit/System Verification

Caution: To help avoid personal injury, additional precautions must be taken prior to working on the generator control module or the generator starter. After removing the 36V battery cables from the generator battery, remove both engine wiring harness connectors from the generator control module. Wait at least 5 minutes and then remove the generator control module cover. Verify voltage levels at all 36V, 12V, and 3-phase connections, are less than 3 volts using a DMM before proceeding.

P1A8D, P1A8E

If DTC is current, replace the SGCM.

Repair Instructions

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