P1A92

DTC P1A91 or P1A92

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 P1A91
- 14 Volt Power Module Temperature Sensor Circuit Low Voltage

DTC P1A92
- 14 Volt Power Module Temperature Sensor Circuit High Voltage

Circuit/System Description

The auxiliary power module (APM) temperature sensor is used for overheat protection. The thermistor is located on the control board, near the phase APM power MOSFET. The starter/generator control module (SGCM) monitors the APM temperature sensor for the following:

* To detect if the APM temperature sensor is shorted low.
* To detect if the APM temperature sensor is shorted high.

If one of the above conditions is detected, the SGCM will set the appropriate DTC.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P1A91

FET temperature sensor signal for APM is less than 0.2 volt for 1 second.

P1A92

APM temperature sensor output voltage is greater than 4.6 volts (-14°C or 6.8°F) and APM temperature is greater than 55°C (131°F) for 1 second.

Action Taken When the DTC Sets

P1A91, P1A92

APM 50 percent maximum current output

Conditions for Clearing the DTC

P1A91, P1A92

Normal range for 10 seconds

Diagnostic Aids

P1A91

Possible APM temperature sensor short to ground or open

P1A92

Possible APM temperature sensor short to voltage

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.

P1A91, P1A92

If DTC is current, replace the SGCM.

Repair Instructions

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