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 P1A7B: Starter/Generator Control Module Temperature Sensor Performance

Circuit/System Description

The starter/generator control module (SGCM) monitors the temperature sensors to determine if the sensor is reading correctly, by comparing it to average of 3 other sensors after 480 minute soak.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The average (PIMTEMP 1, PIMTEMP 2, APMTEMP) - BOARDTEMP is greater than 30°C (86°F)

Action Taken When the DTC Sets

    • 50 percent maximum torque limit
    • APM 50 percent maximum current output

Conditions for Clearing the DTC

Return to normal range for 10 seconds.

Diagnostic Aids

    • Possible internal failure of the temperature sensor
    •  Restricted radiator air flow
    •  Restricted engine coolant flow
    •  Faulty thermostat
    •  Faulty engine water pump
    •  Inoperative SGCM coolant pump

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

  1. Verify the SGCM coolant pump operates.
  2. Ignition ON, command the scan tool SGCM coolant pump output control ON and OFF.
  3. If the SGCM coolant pump does not operate refer to SGCM Coolant Pump Malfunction.
  4. Ignition ON, observe the scan tool SGCM temperature sensor parameters.
  5. If only the SGCM board temperature sensor reads high, replace the SGCM.

Circuit/System Testing

SGCM Coolant Pump Malfunction

  1. Ignition OFF, disconnect the harness connector at the SGCM coolant pump.
  2. Ignition ON, test for B+ between the B+ circuit terminal A and ground.
  3. If less than the specified value, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, connect a test lamp between the B+ circuit terminal A and the control circuit terminal B.
  5. Ignition ON, command the SGCM Coolant Pump Relay ON and OFF with a scan tool. The test lamp should turn On and OFF when commanded.
  6. If the test lamp does not turn ON and OFF when commanded, test the control circuit for an open/high resistance. If the circuit tests normal, replace the SGCM
  7. If all circuits test normal, test or replace the SGCM coolant pump

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Generator Control Module Coolant Pump Replacement
    •  Control Module References for SGCM replacement, setup, and programming