P1A91

DTC P1A91 or P1A92

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 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


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.


P1A91, P1A92

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