AutoCodes – Buick – B3821 Buick

B3821 Buick Code - Left Rear Window Relay Power Circuit

Quick Answer

Battery positive voltage is supplied to the left rear power window switch and the up and down relays through the window lockout signal circuit. Common causes include Faulty Body Control Module (BCM), Body Control Module (BCM) harness is open or shorted, Body Control Module (BCM) 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: B3821 Buick indicates Left Rear Window Relay Power Circuit.
Common causes: Common causes include Faulty Body Control Module (BCM), Body Control Module (BCM) harness is open or shorted, Body Control Module (BCM) 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 439

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Mar 17, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code B3821 Buick Description

Battery positive voltage is supplied to the left rear power window switch and the up and down relays through the window lockout signal circuit. If the window lockout function is disabled, the Body Control Module (BCM) supplies battery positive voltage to the switch and relays and the left rear window operates normally. If the window lockout function is enabled, the BCM will not supply battery positive voltage to the switch and relays and the left rear window will be inoperative unless it is operated from the driver power window switch. The Diagnostic Trouble Code (DTC) sets when the window lockout function is disabled and the window lockout signal circuit is shorted to ground.

OBDII Code B3821 Buick - Left Rear Window Relay Power Circuit - AutoCodes.com — B3821 Buick Code - Left Rear Window Relay Power Circuit

What does this mean?

What are the Possible Causes of the DTC B3821 Buick?

Faulty Body Control Module (BCM)
Body Control Module (BCM) harness is open or shorted
Body Control Module (BCM) circuit poor electrical connection

How to Fix the DTC B3821 Buick?

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 B3821 Buick 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.