P1AA7

DTC P1AA7

Diagnostic Instructions

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

DTC Descriptor
DTC P1AA7
- Starter/Generator Field Coil Circuit

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 DTC will set.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

Field coil current - command current is greater than 0.5 Amp for 1 second.

Action Taken When the DTC Sets

Stop PWM (MGU shutdown).

Conditions for Clearing the DTC

Clears 30 seconds after cycle wakeup signal.

Circuit/System Testing

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. Verify that the latest service software is installed.
2. Disconnect harness connector C2 from the SGCM.
3. Using the appropriate test adapters, test for 5 - 100 ohms resistance between terminals 9 and 12.

• If within the specified range, replace the SGCM.

4. Disconnect the 7 pin connector at the MGU.
5. Test for less than 1 ohm between SGCM connector harness terminal 12 and the MGU connector harness terminal A.

• If less than the specified range, repair the open circuit.

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

• If less than the specified range, repair the open circuit.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Generator with Starter Replacement.

Control Module References for SGCM replacement, setup, and programming.