P1A21

DTC P1A21

Diagnostic Instructions

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

DTC Descriptor
DTC P1A21
- Hybrid Battery Contactor Control Sequence Incorrect

Circuit/System Description

The drive motor generator battery control module is also referred to as the battery energy control module (BECM). The drive motor generator battery control module will diagnose its own systems and determine when a fault condition is present. Diagnostics and system status is communicated from the drive motor generator battery control module to the hybrid powertrain control module (HPCM) through serial data. The hybrid powertrain control module is the host controller for diagnostic trouble code (DTC) information.

The hybrid powertrain control module controls the operation of the high voltage contactors through communication with the drive motor generator battery control module. The hybrid powertrain control module utilizes a pulse width modulated (PWM) contactor system request circuit and redundant serial data to command the high voltage contactors Open and Closed. Under normal operating conditions, the drive motor generator battery control module opens and closes the high voltage contactors based only upon the hybrid powertrain control module command. This diagnostic identifies when the drive motor generator battery control module has opened the high voltage contactors when the hybrid powertrain control module is commanding them closed.

Conditions for Running the DTC

* The vehicle power mode is RUN.
* Ignition voltage is 9-18 V.
* The vehicle has passed a successful precharge and the high voltage contactors have been closed this ignition cycle.
* The hybrid powertrain control module is commanding the drive motor generator battery control module to keep the high voltage contactor closed.

Conditions for Setting the DTC

The drive motor generator battery control module reports that the contactors are open when the hybrid powertrain control module contactor system request circuit and the serial data message both indicate a closed request.

Action Taken When the DTC Sets

DTC P1A21 is a Type A DTC.

Conditions for Clearing the DTC

DTC P1A21 is a Type A DTC.

Diagnostic Aids

* The drive motor generator battery control module will set Contactor System Status parameter to OPEN when the Contactor System Request Circuit Command parameter percent duty cycle is 65-75 percent.
* The drive motor generator battery control module will set Contactor System Status parameter to CLOSED when the Contactor System Request Circuit Command parameter percent duty cycle is 25-35 percent.

Reference Information
Schematic Reference

Hybrid Energy Storage Schematics [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views Connector End Views By Name
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Programming and Relearningfor scan tool information

Circuit/System Verification

1. Verify that DTC P1AE4, P0A80, P1ABE, or P1A0C is not set.

• If any of the DTCs are set, Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Verify that DTC P1A21 is not set.

• If DTC P1A21 is set, replace the drive motor generator battery control module.

Repair Instructions

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

Control Module References Programming and Relearningfor drive motor generator battery control module replacement, setup and programming