AutoCodes – Generic – B3874

B3874 Code - Wiper Low Speed Relay Circuit

Quick Answer

The Body Control Module (BCM) controls and monitors the state of the wiper control circuit. Common causes include Faulty Wiper Low Speed Relay, Wiper Low Speed Relay harness is open or shorted, Wiper Low Speed 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: B3874 indicates Wiper Low Speed Relay Circuit.
Common causes: Common causes include Faulty Wiper Low Speed Relay, Wiper Low Speed Relay harness is open or shorted, Wiper Low Speed 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 915

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 23, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code B3874 Description

The Body Control Module (BCM) controls and monitors the state of the wiper control circuit. When the windshield wiper switch is placed in to a low speed setting, a signal is applied to the BCM. The BCM then applies the battery positive voltage to the coil side of the relay through the relay control circuit. The Diagnostic Trouble Code (DTC) sets when the ignition is in the ON position or the ignition voltage is between 9-16 volts.

OBDII Code B3874 - Wiper Low Speed Relay Circuit - AutoCodes.com — B3874 Code - Wiper Low Speed Relay Circuit

What does this mean?

What are the Possible Causes of the DTC B3874?

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

How to Fix the DTC B3874?

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 B3874 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 B3874 code?

Need more information on how to fix the B3874 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B3874 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B3874 Buick — Wiper Low Speed Relay Circuit
B3874 Cadillac — Wiper Low Speed Relay Circuit
B3874 Chevrolet — Wiper Low Speed Relay Circuit
B3874 GMC — Wiper Low Speed Relay Circuit

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 B3874 Code

1. What are the common symptoms of OBDII code B3874 (Wiper Low Speed Relay Circuit)?

The common symptoms include the wipers not functioning at low speed, erratic wiper movement, or the wipers getting stuck.

2. What are the possible causes of OBDII code B3874?

The code B3874 can be triggered by a faulty wiper low-speed relay, damaged wiring or connectors in the wiper circuit, or a malfunctioning wiper motor.

3. How can I diagnose the issue related to OBDII code B3874?

To diagnose the issue, you can use a scan tool to retrieve the trouble code. Inspect the wiper relay, check the wiring for any signs of damage, and test the wiper motor for proper functioning.

4. Can I repair OBDII code B3874 on my own?

If you have experience with automotive electrical systems, you may be able to repair the issue yourself by replacing the faulty wiper relay, repairing damaged wiring, or replacing the wiper motor if necessary.

5. Are there any simple troubleshooting steps I can try before seeking professional help for OBDII code B3874?

You can start by checking the wiper fuse, ensuring the wiper switch is functioning correctly, and inspecting the wiper blades for any obstructions that may be causing the issue.

6. Will driving with OBDII code B3874 cause any further damage to my vehicle?

Continuing to drive with code B3874 may lead to further wiper malfunction, which could compromise visibility during adverse weather conditions. It is recommended to address the issue promptly.

7. How much does it typically cost to repair OBDII code B3874?

The cost of repairing OBDII code B3874 can vary depending on the underlying cause of the issue, the cost of parts, and labor rates. It is advisable to get a few quotes from automotive repair shops for an accurate estimate.

8. Is it safe to drive my vehicle with OBDII code B3874 if the wipers are still functioning at high speed?

While it may be safe to drive in certain conditions, it is not recommended to ignore the issue as it can lead to complete wiper failure. It is best to address the problem as soon as possible.

9. Can extreme weather conditions contribute to triggering OBDII code B3874?

Yes, extreme weather conditions such as heavy rain, snow, or ice can put additional strain on the wiper system, potentially leading to issues with the wiper low-speed relay circuit.

10. How long does it typically take to repair OBDII code B3874?

The repair time for OBDII code B3874 can vary depending on the complexity of the issue and the availability of parts. In general, a skilled technician can address the problem within a few hours to a day.