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 P0A37: Starter/Generator Temperature Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Signal

P0A38

P0A39

P0A39

--

Low reference

--

P0A39

--

--

Circuit/System Description

The starter/generator control module (SGCM) monitors the performance of the motor generator temperature sensor to detect if it is within range of the other temperature sensors, by comparing it to other temperature sensors it controls.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

Power inverter module (PIM) TEMP 1, PIM TEMP 2, auxiliary power module (APM) TEMP, Board TEMP, motor/generator unit (MGU) TEMP greater than 30°C (80°F) and engine OFF timer greater than 480 minutes of start up.

Action Taken When the DTC Sets

Hybrid system torque will be limited to 50 percent

Conditions for Clearing the DTC

The MGU temperature sensor returns normal range for 10 seconds

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 Testing

  1. Verify DTCs P0A38 or P0A39 are not set.
  2. If P0A38 or P0A39 are set diagnose those first.
  3. Ignition OFF, disconnect harness connectors from the SGCM. Refer to Generator Control Module Replacement
  4. Test for 120 - 125 kohms between the signal circuit SGCM X2 terminal 2 and the low reference circuit terminal 14.
  5. If within the specified range , replace the SGCM.
  6. Disconnect the 7 pin X1 connector at the MGU. Refer to Generator with Starter Replacement
  7. Test for infinite resistance between the SGCM X2 connector terminal 2 and ground.
  8. If less than the specified value, test the circuit for short to ground.
  9. Test for less than 1 ohm between the SGCM X2 connector terminal 2 and the MGU X1 connector terminal G.
  10. If greater than the specified value, test the circuit for an open/high resistance.
  11. Test for less than 1 ohm between SGCM X2 connector terminal 14 and the MGU X1 connector terminal F.
  12. If greater than the specified value, test the circuit for an open/high resistance.
  13. If circuits test normal, replace the MGU.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Generator with Starter Replacement for MGU replacement
    •  Control Module References for SGCM replacement, setup, and programming