AutoCodes – Generic – B3894

B3894 Code - Stop Lamp Switch Circuit Plausibility Failure

Quick Answer

The Body Control Module (BCM) monitors the Stop Lamp Switch Circuit. Common causes include Faulty Stop Lamp Switch Circuit, Stop Lamp Switch Circuit harness is open or shorted, Stop Lamp Switch Circuit 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: B3894 indicates Stop Lamp Switch Circuit Plausibility Failure.
Common causes: Common causes include Faulty Stop Lamp Switch Circuit, Stop Lamp Switch Circuit harness is open or shorted, Stop Lamp Switch Circuit 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 2,426

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 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B3894 Description

The Body Control Module (BCM) monitors the Stop Lamp Switch Circuit. The BCM sets the OBDII code when the Stop Lamp Switch Circuit is not to factory specifications.

OBDII Code B3894 - Stop Lamp Switch Circuit Plausibility Failure - AutoCodes.com — B3894 Code - Stop Lamp Switch Circuit Plausibility Failure

What does this mean?

What are the Possible Causes of the DTC B3894?

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

How to Fix the DTC B3894?

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 B3894 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.

Need more information about the B3894 code?

Need more information on how to fix the B3894 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B3894 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B3894 Buick — Stop Lamp Switch Circuit Plausibility Failure
B3894 Cadillac — Stop Lamp Switch Circuit Plausibility Failure
B3894 Chevrolet — Stop Lamp Switch Circuit Plausibility Failure
B3894 GMC — Stop Lamp Switch Circuit Plausibility Failure

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 B3894 Code

1. What are the common symptoms of OBDII code B3894 (Stop Lamp Switch Circuit Plausibility Failure)?

- Common symptoms include the brake lights staying on or not functioning properly, the cruise control not working, and the inability to shift out of park.

2. What are the possible causes of OBDII code B3894?

- The code B3894 may be triggered by a faulty stop lamp switch, wiring issues in the stop lamp circuit, or a malfunctioning brake pedal position sensor.

3. How can I diagnose the cause of OBDII code B3894?

- To diagnose the issue, you can start by checking the stop lamp switch for proper operation, inspecting the wiring for any damage or loose connections, and testing the brake pedal position sensor.

4. Can I continue driving with OBDII code B3894 present?

- It is not recommended to drive with code B3894 active, as it can affect the proper functioning of your brake lights and other related systems, compromising your safety on the road.

5. How can I repair OBDII code B3894?

- Repairing code B3894 may involve replacing the faulty stop lamp switch, repairing damaged wiring, or recalibrating the brake pedal position sensor. It is advisable to seek professional assistance for accurate diagnosis and repair.

6. Will resetting the OBDII code B3894 resolve the issue?

- Simply resetting the code may temporarily turn off the warning light, but it will not fix the underlying issue causing code B3894. It is important to address the root cause of the problem to prevent it from recurring.

7. Are there any DIY tips for troubleshooting OBDII code B3894?

- You can start by checking the stop lamp switch adjustment, inspecting the fuse related to the stop lamp circuit, and testing the brake pedal position sensor's signal output to troubleshoot code B3894.

8. How long does it take to repair OBDII code B3894?

- The repair time for code B3894 can vary depending on the specific cause of the issue. It may take anywhere from 30 minutes to a few hours to diagnose and repair the problem, depending on the complexity of the repair.

9. Can extreme weather conditions trigger OBDII code B3894?

- Extreme temperatures or weather conditions can sometimes affect the operation of electrical components in the stop lamp circuit, potentially leading to the triggering of code B3894. Inspecting the components during such conditions may help in diagnosis.

10. Is it necessary to use an OBDII scanner to diagnose code B3894?

- Using an OBDII scanner is essential to retrieve the specific code B3894 and further diagnostic information related to the issue. The scanner allows for accurate diagnosis and monitoring of the system's status after repairs.