P1A21 - Hybrid Battery Contactor Control Sequence Incorrect

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3   
Comments  |  Add Comment

Possible causes

  • Faulty Drive Motor Generator Battery Control Module
  • Drive Motor Generator Battery Control Module harness is open or shorted
  • Drive Motor Generator Battery Control Module circuit poor electrical connection

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P1a21 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.

OBDII Code P1a21 - Hybrid Battery Contactor Control Sequence Incorrect - AutoCodes.com

P1A21 Information for specific makes

  • P1A21 BUICK Hybrid Battery Contactor Control Sequence Incorrect
  • P1A21 CADILLAC Hybrid Battery Contactor Control Sequence Incorrect
  • P1A21 CHEVROLET Hybrid Battery Contactor Control Sequence Incorrect
  • P1A21 GMC Hybrid Battery Contactor Control Sequence Incorrect

Need more help?

Get the P1a21 code diagnosed by a professional: Find a repair shop in your area

Related Information

P1A21 Comments

Help us improve AutoCodes.com. Leave a comment below or tell us if the information above help you fix the code. What are the symptoms on your vehicle for the P1a21 code? Have you replaced any parts?
Any information is appreciated. Thanks
Top ⇧