OBD Guide
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C121D

Brake Pressure Sensor Circuit

C121D is an OBD-II diagnostic trouble code meaning: Brake Pressure Sensor Circuit. Common causes: open or short circuit in wiring harness, brake pressure sensor malfunction. Estimated repair cost: $56–167.

Severity
🔴 High
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$56–167 (est.)

Symptoms

  • The brake system fault indicator is on
  • Disabling the ABS or ESP system
  • Unstable brake operation

Causes

  • Open or short circuit in wiring harness
  • Brake pressure sensor malfunction
  • Poor contact in the sensor connector
  • Problems with the brake ECU

How to Fix

  1. Check the integrity of the sensor wiring harness
  2. Check sensor connectors for oxidation or damage.
  3. Test the brake pressure sensor with a multimeter
  4. If necessary, replace the sensor or wiring harness
  5. Reset the error and check the system

Related codes

C121CC121EC1220

FAQ

What does the C121D code mean?

C121D is an OBD-II diagnostic trouble code that indicates: Brake Pressure Sensor Circuit

What causes a C121D error code?

The most common causes of C121D include: Open or short circuit in wiring harness; Brake pressure sensor malfunction; Poor contact in the sensor connector; Problems with the brake ECU.

How do I fix a C121D diagnostic trouble code?

To fix C121D: Check the integrity of the sensor wiring harness. Check sensor connectors for oxidation or damage.. Test the brake pressure sensor with a multimeter. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C121D?

Limited driving only, diagnose soon

How much does it cost to fix C121D?

The estimated repair cost for C121D is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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