P1A90

DTC P1A90

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 P1A90
- 14 Volt Power Module Temperature Sensor Performance

Circuit/System Description

The starter/generator control module (SGCM) monitors to detect the failure of the auxiliary power module (APM) temperature sensor circuit by taking the average of the 2 power inverter module (PIM) sensors and subtracting the module temperature and looking for a difference.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

APM temperature sensor is greater than 55 degrees Celsius (131 degrees Fahrenheit) for 2 seconds.

Action Taken When the DTC Sets

APM 50 percent maximum current output.

Conditions for Clearing the DTC

Voltage limit returns to normal range for 10 seconds.

Diagnostic Aids

Possible internal failure at temperature sensor.

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.

1. If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics
2. If DTC is current, replace the starter/generator control module (SGCM).

Repair Instructions

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

Control Module References for SGCM replacement, setup, and programming.