AutoCodes – Mercury – B0004 Mercury

B0004 Mercury Code - Driver Knee Bolster Deployment Control

Quick Answer

The Restraints Control Module (RCM) monitors all deployable device and sensor circuits for a signal cross coupled (short) between circuits. Common causes include Faulty Driver Knee Airbag, Driver Knee Airbag harness is open or shorted, Driver Knee Airbag 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: B0004 Mercury indicates Driver Knee Bolster Deployment Control.
Common causes: Common causes include Faulty Driver Knee Airbag, Driver Knee Airbag harness is open or shorted, Driver Knee Airbag 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 3,752

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 Nov 18, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0004 Mercury Description

The Restraints Control Module (RCM) monitors all deployable device and sensor circuits for a signal cross coupled (short) between circuits. If the RCM detects a short between the circuits of one device and another device, it will store a DTC for each of the signal cross coupled faults in memory. The RCM sends a message to the Instrument Panel Cluster (IPC) to illuminate the air bag warning indicator. When a normal loop fault is present (one loop is either shorted to battery/ground, open circuit or low resistance), then signal cross coupled diagnostics will not be active. Once the normal loop fault is repaired, then the signal cross coupled diagnostics will resume.

OBDII Code B0004 Mercury - Driver Knee Bolster Deployment Control - AutoCodes.com — B0004 Mercury Code - Driver Knee Bolster Deployment Control

What does this mean?

What are the Possible Causes of the DTC B0004 Mercury?

Faulty Driver Knee Airbag
Driver Knee Airbag harness is open or shorted
Driver Knee Airbag circuit poor electrical connection

How to Fix the DTC B0004 Mercury?

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 B0004 Mercury 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 B0004 Mercury code?

Need more information on how to fix the B0004 Mercury code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B0004 Mercury code diagnosed by a professional: Find a repair shop in your area

Precautions for SRS “AIR BAG” and “SEAT BELT PRE-TENSIONER” Service

Never probe the electrical connectors on air bag, side air curtain modules or seat belts.
Never disassemble or tamper with safety belt buckle/retractor pretensioners, adaptive load limiting retractors, safety belt inflators, or probe the electrical connectors.
Do not use electrical test equipment to check SRS circuits unless instructed to in this Service Manual.
Before servicing the SRS, turn ignition switch OFF, disconnect both battery cables and wait at least 3 minutes. For approximately 3 minutes after the cables are removed, it is still possible for the air bag and seat belt pre-tensioner to deploy. Therefore, do not work on any SRS connectors or wires until at least 3 minutes have passed.

Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.

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 B0004 Mercury Code

1. What does OBDII code B0004 for Mercury mean?

The code B0004 on a Mercury indicates an issue with the Driver Knee Bolster Deployment Control, specifically related to the deployment control circuit.

2. What are the common symptoms of OBDII code B0004 in a Mercury?

Common symptoms of code B0004 in a Mercury may include the airbag warning light illuminating on the dashboard and potential issues with the deployment of the driver knee bolster in the event of a collision.

3. What are the possible causes of OBDII code B0004 in a Mercury?

The code B0004 in a Mercury may be triggered by a faulty driver knee bolster deployment control module, damaged wiring or connectors in the system, or a malfunction in the driver knee bolster itself.

4. How can I diagnose the OBDII code B0004 in my Mercury?

Diagnosing code B0004 in a Mercury typically involves using a professional OBDII scanner to retrieve the specific fault code, inspecting the driver knee bolster deployment control module, and checking the related wiring and connectors for any visible damage.

5. Can I continue driving my Mercury with OBDII code B0004 present?

It is not recommended to continue driving your Mercury with OBDII code B0004 present, as this indicates a potential issue with the driver knee bolster deployment system, which is crucial for occupant safety in the event of a collision.

6. How can I repair OBDII code B0004 in my Mercury?

Repairing OBDII code B0004 in a Mercury may involve replacing the faulty driver knee bolster deployment control module, repairing or replacing damaged wiring or connectors, and ensuring the system is functioning properly through thorough testing.

7. Do I need special tools to fix OBDII code B0004 in my Mercury?

Repairing OBDII code B0004 in a Mercury may require specialized tools such as an OBDII scanner for diagnosis, as well as basic hand tools for accessing and working on the driver knee bolster deployment control module and related components.

8. Is it safe to reset the OBDII code B0004 in my Mercury without fixing the issue?

It is not advisable to simply reset the OBDII code B0004 in your Mercury without addressing the underlying issue, as this may compromise the proper functioning of the driver knee bolster deployment system and jeopardize occupant safety.

9. Can a DIY enthusiast fix OBDII code B0004 in a Mercury at home?

While some DIY enthusiasts may have the skills to diagnose and repair OBDII code B0004 in a Mercury, it is recommended to seek professional help, especially when dealing with critical safety systems like the driver knee bolster deployment control.

10. How much does it cost to repair OBDII code B0004 in a Mercury at a dealership or repair shop?

The cost of repairing OBDII code B0004 in a Mercury at a dealership or repair shop can vary depending on the specific issue, parts needed for replacement, labor costs, and any additional diagnostics required. It is advisable to get a detailed estimate before proceeding with the repairs.