AutoCodes – Generic – C121D

C121D Code - Brake Pressure Sensor Circuit

Quick Answer

The Anti-Lock Brake System (ABS) Module monitors the Brake Pressure Sensor. Common causes include Faulty Brake Master Cylinder, Faulty Brake Booster, Faulty Anti-Lock Brake System (ABS) Module. 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: C121D indicates Brake Pressure Sensor Circuit.
Common causes: Common causes include Faulty Brake Master Cylinder, Faulty Brake Booster, Faulty Anti-Lock Brake System (ABS) Module.
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 8,410

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 Aug 25, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code C121D Description

The Anti-Lock Brake System (ABS) Module monitors the Brake Pressure Sensor. The ABS Module sets the OBDII code when the Brake Pressure Sensor is not to factory specifications.

OBDII Code C121D - Brake Pressure Sensor Circuit - AutoCodes.com — C121D Code - Brake Pressure Sensor Circuit

What does this mean?

What are the Possible Causes of the DTC C121D?

Faulty Brake Master Cylinder
Faulty Brake Booster
Faulty Anti-Lock Brake System (ABS) Module
Anti-Lock Brake System (ABS) Module harness is open or shorted
Anti-Lock Brake System (ABS) Module circuit poor electrical connection

How to Fix the DTC C121D?

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 C121D 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 C121D code?

Need more information on how to fix the C121D code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the C121D code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

C121D Chrysler — Brake Pressure Sensor Circuit
C121D Dodge — Brake Pressure Sensor Circuit
C121D Jeep — Brake Pressure Sensor Circuit
C121D Mitsubishi — Brake Fluid Pressure Sensor 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 C121D Code

1. What are the common symptoms of OBDII code C121D (Brake Pressure Sensor Circuit)?

- Common symptoms include the ABS warning light illuminated on the dashboard, decreased brake performance, and potential activation of the vehicle's traction control system.

2. What are the typical causes of OBDII code C121D?

- The code C121D is often triggered by a faulty brake pressure sensor, damaged wiring or connectors in the sensor circuit, or issues with the ABS control module.

3. How can I diagnose the cause of OBDII code C121D?

- Diagnosing code C121D involves using a professional OBDII scanner to read the code, visually inspecting the brake pressure sensor and its connections, and conducting electrical tests to determine if the sensor is functioning correctly.

4. Is it safe to drive with OBDII code C121D active?

- It is not recommended to drive with OBDII code C121D present, as it may affect the proper functioning of the vehicle's braking system, potentially compromising safety.

5. How can I repair OBDII code C121D (Brake Pressure Sensor Circuit) myself?

- DIY repair options include checking and cleaning the sensor connectors, inspecting for any damaged wiring, and replacing the brake pressure sensor if necessary. However, it is recommended to have a professional technician diagnose and repair the issue for optimal safety.

6. Can a faulty brake pressure sensor cause other issues in the vehicle?

- Yes, a faulty brake pressure sensor can impact the overall performance of the vehicle's ABS system, traction control system, and potentially affect brake responsiveness and safety.

7. How much does it typically cost to repair OBDII code C121D?

- The cost of repairing OBDII code C121D can vary depending on the root cause of the issue, but it may range from $200 to $500, including parts and labor.

8. What should I do if I reset the OBDII code C121D and it returns?

- If you reset the code and it returns, it indicates that the underlying issue still persists. It is crucial to have the brake pressure sensor circuit thoroughly inspected and repaired by a qualified mechanic.

9. Can OBDII code C121D affect the vehicle's emissions or fuel efficiency?

- While code C121D itself may not directly impact emissions or fuel efficiency, ignoring the issue can lead to further damage to the braking system, potentially affecting overall vehicle performance and safety.

10. Is it necessary to have the ABS system recalibrated after repairing OBDII code C121D?

- It is advisable to have the ABS system recalibrated after repairing OBDII code C121D to ensure that the braking system functions correctly and the warning light is reset.