AutoCodes – Mercury – B1921 Mercury

B1921 Mercury Code - RCM Bracket Ground Resistance High

Quick Answer

The Restraint Control Module (RCM) monitors resistance between ground connections at its housing and reference ground at RCM connector. Common causes include Faulty Restraint Control Module (RCM), Restraint Control Module (RCM) harness is open or shorted, Restraint Control Module (RCM) 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: B1921 Mercury indicates RCM Bracket Ground Resistance High.
Common causes: Common causes include Faulty Restraint Control Module (RCM), Restraint Control Module (RCM) harness is open or shorted, Restraint Control Module (RCM) 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 928

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 Jul 28, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B1921 Mercury Description

The Restraint Control Module (RCM) monitors resistance between ground connections at its housing and reference ground at RCM connector. If RCM detects resistance more than 100 ohms, it stores Diagnostic Trouble Code (DTC) B1921 in memory and flashes on AIR BAG warning light.

OBDII Code B1921 Mercury - RCM Bracket Ground Resistance High - AutoCodes.com — B1921 Mercury Code - RCM Bracket Ground Resistance High

What does this mean?

What are the Possible Causes of the DTC B1921 Mercury?

Faulty Restraint Control Module (RCM)
Restraint Control Module (RCM) harness is open or shorted
Restraint Control Module (RCM) circuit poor electrical connection

How to Fix the DTC B1921 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 B1921 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 B1921 Mercury code?

Need more information on how to fix the B1921 Mercury code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1921 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 B1921 Mercury Code

1. What are the common symptoms of OBDII code B1921 (RCM Bracket Ground Resistance High) in a Mercury vehicle?

- The common symptoms include the airbag warning light illuminating on the dashboard and potential issues with the airbag system's functionality.

2. What could be the possible causes of OBDII code B1921 in a Mercury vehicle?

- The code B1921 typically indicates a high resistance in the Restraints Control Module (RCM) bracket ground circuit, which could be caused by a loose connection, damaged wiring, or a faulty ground point.

3. How can I diagnose the high ground resistance issue related to OBDII code B1921 in my Mercury?

- To diagnose the issue, you can perform a visual inspection of the wiring and connectors related to the RCM bracket ground. Using a multimeter to check for continuity and resistance in the circuit can help pinpoint the exact location of the high resistance.

4. Is it safe to drive my Mercury with OBDII code B1921 (RCM Bracket Ground Resistance High) present?

- It is not recommended to drive the vehicle with an active airbag system fault code like B1921, as it may affect the proper deployment of the airbags in case of an accident. It is advised to address the issue promptly.

5. Can I reset the OBDII code B1921 in my Mercury without fixing the underlying issue?

- While you can clear the code temporarily with an OBDII scanner, it is crucial to address the root cause of the high ground resistance to prevent the code from reoccurring and ensure the proper functioning of the airbag system.

6. What are some repair tips for fixing OBDII code B1921 in a Mercury due to RCM bracket ground resistance high?

- Repair tips may include checking and tightening the ground connections, repairing or replacing damaged wiring, and ensuring proper grounding of the RCM bracket to resolve the high resistance issue.

7. Can a DIY enthusiast fix OBDII code B1921 in a Mercury, or is professional help necessary?

- Depending on your level of automotive repair experience, fixing OBDII code B1921 may be possible for a DIY enthusiast, especially if it involves basic tasks like checking connections and wiring. However, if you are unsure or uncomfortable with the repair process, seeking professional help is recommended.

8. How much can I expect to pay for repairing OBDII code B1921 (RCM Bracket Ground Resistance High) in a Mercury at a repair shop?

- The cost of repairing OBDII code B1921 can vary depending on the exact cause of the high ground resistance and the labor rates of the repair shop. It is advisable to obtain quotes from different shops for an accurate estimate.

9. Will fixing OBDII code B1921 in my Mercury require replacing any parts, or can it be resolved through maintenance and repairs?

- In most cases, resolving OBDII code B1921 (RCM Bracket Ground Resistance High) in a Mercury involves maintenance tasks like checking connections, repairing wiring, and ensuring proper grounding. Parts replacement may be necessary if any components are found to be faulty.

10. How long does it typically take to repair OBDII code B1921 in a Mercury caused by RCM bracket ground resistance high?

- The repair time for OBDII code B1921 can vary based on the extent of the issue and the repair process involved. It may range from a quick fix taking a few hours to a more complex repair requiring a day or more, especially if wiring needs to be replaced.