P1A90

DTC P1A90

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)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°C (131°F) 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


Reference Information
Schematic Reference

Hybrid Controls Schematics ()
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for Scan Tool Information


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.


If DTC is current, replace the SGCM.


Repair Instructions

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


Control Module References (Programming and Relearning)for SGCM replacement, setup, and programming