AutoCodes – Chevrolet – P1A21 Chevrolet

P1A21 Chevrolet Code - Hybrid Battery Contactor Control Sequence Incorrect

Quick Answer

The drive motor generator battery control module is also referred to as the Battery Energy Control Module (BECM). Common causes include 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. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1A21 Chevrolet indicates Hybrid Battery Contactor Control Sequence Incorrect.
Common causes: Common causes include 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.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 1,464

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Feb 15, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P1A21 Chevrolet 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 Chevrolet - Hybrid Battery Contactor Control Sequence Incorrect - AutoCodes.com — P1A21 Chevrolet Code - Hybrid Battery Contactor Control Sequence Incorrect

What does this mean?

What are the Possible Causes of the DTC P1A21 Chevrolet?

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

How to Fix the DTC P1A21 Chevrolet?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1A21 Chevrolet code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.