Hybrid Energy Storage

DTC P0AA2

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 P0AA2
- Hybrid Battery Positive Contactor Circuit Stuck Open

Circuit/System Description

The engine control module (ECM) monitors to detect when it can no longer control the state of the contactor.

Conditions for Running the DTC

Engine ON

Conditions for Setting the DTC

* The diagnostic fails when then the BECM does not respond to the ECMs CLOSE command.
* 3 seconds after the contactor has been commanded to CLOSE, if the contactor status at any time does not read as CLOSED, the diagnostic will fail.
* If the service disconnect is active, the diagnostic will fail.

Action Taken When the DTC Sets

The hybrid system is disabled.

Conditions for Clearing the DTC

* The contactor status is CLOSED while the contactor is commanded to CLOSE.
* The condition responsible for setting the DTC no longer exists.
* The ignition must be cycled before the DTC can be cleared.

Reference Information
Schematic Reference

Hybrid Energy Storage Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Generator Battery Carrier Description and Operation (Description and Operation)
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

Diagnostic Aids

This diagnostic also fails when the BECM refuses to obey the ECM's CLOSE command. The contactor can be reported as Closed, Impact Detected, Service Disconnect, Open, Overtemperature, and Fault, and the BECM sets this status.

If the DTC is current, check the status of the contactor using the scan tool. If the status is Service Disconnect, verify that the service disconnect is fully engaged by the BECM cover when closed. If this diagnostic is accompanied by hybrid battery temperature circuit DTCs, diagnose those DTCs first. If the vehicle was in an event where the airbag deployed, the crash event must be deasserted in vehicle communications before the contactor will be allowed to close. If the contactor status is Fault, then there may be an issue with the battery disconnect unit.

If the DTC is in history with no other faults, or the BECM cover was fully seated, Inspect connections at the BECM harness for X2.

Circuit/System Testing

1. If other DTCs are set diagnose those first.
2. With a scan tool, clear the DTC.
3. Cycle the ignition switch from OFF to RUN several times.
4. Ignition ON, operate the vehicle within the Conditions for Running the DTC and verify the DTC does not reset.

If the DTC resets, replace the BECM.

Repair Instructions

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

Control Module References (Programming and Relearning) for BECM replacement, setup, and programming.