P1AA7

DTC P1AA7

Diagnostic Instructions

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


Diagnostic Aids

This DTC can set falsely when vehicle is keyed off. The DTC is type B, so will not set MIL unless it occurs twice in succession. Refer to Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions). The DTC will not store into history until this occurs. If this DTC is only set in history, clear with scan tool.


Reference Information
Schematic Reference

Hybrid Controls Schematics ()
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for Scan Tool Information


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 X2 from the SGCM. Refer to Generator Control Module Replacement ().
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 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. If both circuits test normal, replace the MGU.



Repair Instructions

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

* Generator with Starter Replacement ()
* Control Module References (Programming and Relearning)for SGCM replacement, setup, and programming