P0AA2

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

When the Ignition is in RUN, the engine running.


Conditions for Setting the DTC

* The diagnostic fails when then the BECM does not resond 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.


Reference Information
Schematic Reference

Hybrid Energy Storage 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


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

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.


Caution: To help avoid personal injury, be careful when working in the vicinity of the generator battery disconnect control module. Internal components will still be live, 36V potential, even when the cover has been opened or removed.


1. If other DTCs are set diagnose those first.
2. Cycle the ignition switch from OFF to RUN several times.


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.