AutoCodes – GMC – B3809 GMC

B3809 GMC Code - Rear Door Unlock Relay Circuit

Quick Answer

The Body Control Module (BCM) internally grounds the door unlock relay control circuit for the rear door unlock relay when it receives a class 2 message from the Driver Door Module (DDM) or passenger door module (PDM). Common causes include Faulty Rear Door Unlock Relay, Rear Door Unlock Relay harness is open or shorted, Rear Door Unlock Relay 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: B3809 GMC indicates Rear Door Unlock Relay Circuit.
Common causes: Common causes include Faulty Rear Door Unlock Relay, Rear Door Unlock Relay harness is open or shorted, Rear Door Unlock Relay 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 830

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 Mar 17, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B3809 GMC Description

The Body Control Module (BCM) internally grounds the door unlock relay control circuit for the rear door unlock relay when it receives a class 2 message from the Driver Door Module (DDM) or passenger door module (PDM). When the BCM grounds the door unlock relay control circuit the rear door unlock relay is energized and unlocks the rear doors. The Diagnostic Trouble Code (DTC) sets if the door unlock relay control circuit is shorted to ground or open for more then one second.

OBDII Code B3809 GMC - Rear Door Unlock Relay Circuit - AutoCodes.com — B3809 GMC Code - Rear Door Unlock Relay Circuit

What does this mean?

What are the Possible Causes of the DTC B3809 GMC?

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

How to Fix the DTC B3809 GMC?

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 B3809 GMC 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.

Frequently Asked Questions about B3809 GMC Code

1. What are the common symptoms of OBDII code B3809 GMC (Rear Door Unlock Relay Circuit)?

- The common symptoms include rear door(s) not unlocking when using the central locking system or key fob, and potential issues with the rear door lock mechanism.

2. What are the possible causes of OBDII code B3809 GMC?

- The code B3809 can be triggered by a faulty rear door unlock relay, damaged wiring in the rear door unlock circuit, or a malfunctioning rear door lock actuator.

3. How can I diagnose the issue related to OBDII code B3809 GMC?

- To diagnose the problem, you can start by checking the rear door unlock relay and related wiring for any visible damage or loose connections. Using a multimeter to test the relay's functionality can also help pinpoint the issue.

4. Is it safe to continue driving with OBDII code B3809 GMC active?

- While the vehicle may still be drivable with this code, it is recommended to address the issue promptly to ensure proper functioning of the rear door locking system for safety and convenience.

5. Can I repair OBDII code B3809 GMC on my own?

- Depending on your automotive repair skills, you may be able to address the issue yourself by replacing the rear door unlock relay or repairing any damaged wiring. However, seeking professional help is advised if you are unsure.

6. Are there any quick temporary fixes for OBDII code B3809 GMC?

- In some cases, manually unlocking the rear doors using the internal door handles or key may serve as a temporary solution until the root cause of the issue is identified and repaired.

7. How much does it typically cost to repair OBDII code B3809 GMC?

- The cost of repairing OBDII code B3809 can vary depending on the specific cause of the issue, labor rates in your area, and whether you choose to replace parts yourself or have a mechanic handle the repair.

8. Can extreme weather conditions affect OBDII code B3809 GMC?

- Yes, extreme temperatures or moisture can potentially exacerbate issues with the rear door unlock relay circuit, leading to the triggering of OBDII code B3809 in GMC vehicles.

9. Will resetting the OBDII system clear code B3809 GMC?

- While resetting the OBDII system may temporarily clear the code, it is important to address the underlying issue causing OBDII code B3809 to prevent it from recurring.

10. How can I prevent OBDII code B3809 GMC from happening again in the future?

- Regularly inspecting the rear door lock components, addressing any issues promptly, and avoiding excessive force when operating the rear door locking system can help prevent the recurrence of OBDII code B3809 in GMC vehicles.