GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1A9B: Starter/Generator Inverter Phase U Temperature Sensor Performance

Circuit/System Description

The power inverter module (PIM) temperature 1 sensor is used for overheat protection. The thermistor is located on the control board, near the phase W power MOSFET. The starter/generator control module (SGCM) monitors the inverter temperature sensor to detect the failure of the inverter temperature sensor using rationality of other temperature sensors to determine if it is out of range.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

Inverter temperature sensor is greater than 55°C (131°F) for 2 seconds.

Action Taken When the DTC Sets

50 percent maximum torque limit

Conditions for Clearing the DTC

Normal range for 10 seconds

Diagnostic Aids

Possible internal failure of temperature sensor

Reference Information

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Starter/Generator Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Warning: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.

  1. With a scan tool, clear the DTC.
  2. Ignition OFF, wait 30 seconds.
  3. Ignition ON, operate the vehicle within the Conditions for Running the DTC.
  4. If the DTC resets, replace the SGCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for SGCM replacement, setup, and programming