Diagnostic Instructions

DTC Descriptors

DTC P1AA8: Starter/Generator Field Control Performance

DTC P1AB9: Starter/Generator Field Coil Current Sensor Circuit Low Voltage

DTC P1ABA: Starter/Generator Field Coil Current Sensor Circuit High Voltage

DTC P1ABB: Starter/Generator Field Coil Current Sensor Overcurrent

Circuit/System Description

The starter/generator control module (SGCM) monitors the motor generator unit (MGU) field coil circuit to see if the field coil current is within tolerance. If a fault is detected, the appropriate DTC will set.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

P1AA8

Field coil current - command current is greater than 0.5 A for 1.0 second.

P1AB9

Sensor output voltage less than 1.8 volts (-2 A) for 20 ms.

P1ABA

Sensor output voltage greater than 4.1 volts (10 A) for 20 ms.

P1ABB

Field coil current is greater than 6 A for 20 ms.

Action Taken When the DTC Sets

Stop PWM (MGU shutdown)

Conditions for Clearing the DTC

The DTC will clear 30 seconds after the ignition is turned OFF and then turned back ON, enabling the module cycle wakeup signal.

Diagnostic Aids

P1AA8

Possible cable open or short to ground.

P1AB9, P1ABA

Possible open circuit or faulty cable connection.

P1ABB

Possible short circuit or faulty cable connection.

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Warning: 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. Verify that the latest service software is installed.
2. Disconnect harness connector X2 from the SGCM. Refer to Generator Control Module Replacement.
3. Using the appropriate test adapters, test for 5-100 ohms between terminals 9 and 12.

⇒	If within the specified range, replace the SGCM.

4. Disconnect the 7 pin X1 connector at the MGU. Refer to Generator with Starter Replacement.
5. Test for less than 1 ohm between SGCM connector harness terminal 12 and the MGU X1 connector harness terminal A.

⇒	If greater than the specified value, repair the open circuit.

6. Test for less than 1 ohm between SGCM connector harness terminal 9 and the MGU X1 connector harness terminal C.

⇒	If greater than the specified value, repair the open circuit.

7. Test for no continuity between SGCM connector harness terminal 9 and terminal 12.

⇒	If greater than the specified value, repair the shorted circuits.

8. Test for short between SGCM connector harness terminal 12 and ground.

⇒	If greater than the specified value, repair the shorted circuit.

9. If both circuits test normal, replace the MGU.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.