AutoCodes – Mercury – B0021 Mercury

B0021 Mercury Code - Left Curtain Deployment Control 1

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 Side Air Curtain, Driver Side Air Curtain harness is open or shorted, Driver Side Air Curtain 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: B0021 Mercury indicates Left Curtain Deployment Control 1.
Common causes: Common causes include Faulty Driver Side Air Curtain, Driver Side Air Curtain harness is open or shorted, Driver Side Air Curtain 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 3,373

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 Oct 09, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0021 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 B0021 Mercury - Left Curtain Deployment Control 1 - AutoCodes.com — B0021 Mercury Code - Left Curtain Deployment Control 1

What does this mean?

What are the Possible Causes of the DTC B0021 Mercury?

Faulty Driver Side Air Curtain
Driver Side Air Curtain harness is open or shorted
Driver Side Air Curtain circuit poor electrical connection

How to Fix the DTC B0021 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 B0021 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 B0021 Mercury code?

Need more information on how to fix the B0021 Mercury code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B0021 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 B0021 Mercury Code

1. What are the common symptoms of OBDII code B0021 in a Mercury related to the Left Curtain Deployment Control 1?

- Common symptoms include the airbag warning light being illuminated on the dashboard, along with potential issues with the left side curtain airbag system.

2. What are the possible causes of OBDII code B0021 in a Mercury?

- The code B0021 typically indicates a fault in the left curtain airbag deployment control circuit, which can be caused by issues such as a faulty airbag module, wiring problems, or a malfunctioning impact sensor.

3. How serious is OBDII code B0021 in a Mercury?

- OBDII code B0021 related to the Left Curtain Deployment Control 1 is a serious issue as it involves the safety system of the vehicle. It is important to address this code promptly to ensure the proper functionality of the curtain airbag in the event of a collision.

4. Can I continue driving my Mercury with OBDII code B0021 present?

- It is not recommended to continue driving the vehicle with OBDII code B0021 present, as it indicates a problem with the left curtain airbag system. Driving with a malfunctioning airbag system can compromise safety in the event of an accident.

5. How can I diagnose and repair OBDII code B0021 in my Mercury?

- Diagnosis and repair of OBDII code B0021 require specialized tools and knowledge. It is recommended to have the vehicle inspected by a qualified mechanic who can perform diagnostic tests to pinpoint the exact cause of the issue and make the necessary repairs.

6. Are there any DIY tips for troubleshooting OBDII code B0021 in a Mercury?

- DIY troubleshooting for OBDII code B0021 can be challenging due to the complexity of the airbag system. It is best to leave diagnostic and repair tasks to experienced professionals to ensure the safety and proper functionality of the airbag system.

7. How much does it typically cost to repair OBDII code B0021 in a Mercury?

- The cost of repairing OBDII code B0021 can vary depending on the exact cause of the issue and the labor rates in your area. It is advisable to obtain quotes from different repair shops to compare prices and services.

8. Can resetting the OBDII system clear the B0021 code in a Mercury?

- Resetting the OBDII system may temporarily clear the B0021 code, but it is likely to reappear if the underlying issue with the left curtain airbag deployment control circuit is not addressed. It is important to diagnose and repair the root cause of the problem.

9. Is it possible to prevent OBDII code B0021 from occurring in my Mercury?

- While some causes of OBDII code B0021 may be unavoidable, regular maintenance and inspections of the airbag system can help detect potential issues early and prevent codes like B0021 from occurring.

10. How long does it typically take to repair OBDII code B0021 in a Mercury?

- The repair time for OBDII code B0021 can vary depending on the cause of the issue and the availability of parts. In general, it may take a few hours to a day to diagnose and repair the problem with the left curtain airbag deployment control circuit in a Mercury.