OBD Guide
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C12B4

ABS Master Cylinder Pressure Sensor Performance

C12B4 is an OBD-II diagnostic trouble code meaning: ABS Master Cylinder Pressure Sensor Performance. Common causes: abs master cylinder pressure sensor malfunction, damaged wiring harness or contacts. Estimated repair cost: $56–167.

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

Symptoms

  • The ABS indicator on the dashboard is on
  • Reduced ABS performance
  • Unusual behavior of the braking system (jerking, vibrations)

Causes

  • ABS master cylinder pressure sensor malfunction
  • Damaged wiring harness or contacts
  • Problems with the ABS module
  • Sensor dirty or corroded

How to Fix

  1. Check the condition of the ABS master cylinder pressure sensor
  2. Inspect the wiring harness and contacts for damage
  3. Clean the sensor from dirt
  4. Replace sensor if necessary
  5. Check the operation of the ABS system after repair

Related codes

C12B5C12B6C12B7

FAQ

What does the C12B4 code mean?

C12B4 is an OBD-II diagnostic trouble code that indicates: ABS Master Cylinder Pressure Sensor Performance

What causes a C12B4 error code?

The most common causes of C12B4 include: ABS master cylinder pressure sensor malfunction; Damaged wiring harness or contacts; Problems with the ABS module; Sensor dirty or corroded.

How do I fix a C12B4 diagnostic trouble code?

To fix C12B4: Check the condition of the ABS master cylinder pressure sensor. Inspect the wiring harness and contacts for damage. Clean the sensor from dirt. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C12B4?

Limited driving only, diagnose soon

How much does it cost to fix C12B4?

The estimated repair cost for C12B4 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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