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 Descriptors

DTC P1AB3: Starter/Generator Phase U Current Sensor Circuit Low Voltage

DTC P1AB4: Starter/Generator Phase U Current Sensor Circuit High Voltage

DTC P1AB5: Starter/Generator Phase V Current Sensor Circuit Low Voltage

DTC P1AB6: Starter/Generator Phase V Current Sensor Circuit High Voltage

DTC P1AB7: Starter/Generator Phase W Current Sensor Circuit Low Voltage

DTC P1AB8: Starter/Generator Phase W Current Sensor Circuit High Voltage

Circuit/System Description

The starter/generator control module (SGCM) phase U/V/W current sensors are used for motor control and power inverter module (PIM) current sensor rationality check. The SGCM monitors the current sensor for the following:

    • To detect a failure of the U/V/W-phase current sensor circuit below valid range
    • To detect a failure of the U/V/W-phase current sensor circuit above valid range

If one of the above conditions is detected, the SGCM will set the appropriate DTC.

Conditions for Running the DTC

P1AB3, P1AB4, P1AB5, P1AB6, P1AB7, P1AB8

    • Engine is running.
    • Wakeup signal is ON.

Conditions for Setting the DTC

P1AB3, P1AB5, P1AB7

Sensor output voltage at high side less than 0.5 volt for 0.5 ms

P1AB4, P1AB6, P1AB8

Sensor output voltage at high side greater than 4.5 volts for 0.5 ms

Action Taken When the DTC Sets

P1AB3, P1AB4, P1AB5, P1AB6, P1AB7, P1AB8

    • Stop PWM (MGU shutdown)
    • APM PWM OFF
    • Battery disconnection (disconnect SW on/off)

Conditions for Clearing the DTC

P1AB3, P1AB4

U-phase current sensor circuit within valid range

P1AB5, P1AB6

V-phase current sensor circuit within valid range

P1AB7, P1AB8

W-phase current sensor circuit within valid range

Diagnostic Aids

P1AB3, P1AB5, P1AB7

Possible Electrical failure at current sensor with short to ground or open

P1AB4, P1AB6, P1AB8

Possible electrical failure at current sensor with short to voltage

Reference Information

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Hybrid Controls Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Scan Tool Data List

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.

  1. If DTC is history, refer to Testing for Intermittent Conditions and Poor Connections .
  2. If DTC is current, replace the SGCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for SGCM replacement, setup, and programming