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DTC codes / C05xx · Brakes, steering and suspension / C05C1

C05C1Brake Pedal Position Sensor B Not Learned

The C05C1 code indicates that the brake pedal position sensor B has not completed its calibration learning procedure, so the control module cannot trust its signal for accurate brake pedal position. The computer detected that the sensor's learned zero point or range is missing or invalid, which prevents reliable interpretation of brake pedal travel.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • Illumination of the brake system warning light or a generic check engine light.
  • Often no symptoms besides the warning light, with normal brake pedal feel and operation.
  • Inconsistent or delayed response from brake-related features such as hill-start assist or regenerative braking.
  • Possible disablement of cruise control or adaptive cruise control functions.
  • In some cases, a stored trouble code in the anti-lock brake system (ABS) module without any driver-perceived change.
  • Rarely, a slightly longer pedal travel or a soft pedal if the sensor signal is erratic.

Common causes, most likely first

  1. Brake pedal position sensor B has not been initialized or learned after replacement or battery disconnection.
  2. Sensor B is faulty or has an internal electrical failure preventing a successful learn procedure.
  3. Wiring or connector issues at sensor B, such as corrosion, loose pins, or damaged harness.
  4. The brake pedal position sensor mounting bracket is bent or misaligned, causing the sensor to read out of range.
  5. A low or weak vehicle battery caused the learn procedure to abort or the memory to be lost.
  6. A software glitch or corrupted calibration data in the control module that requires a reflash or relearn.
  7. Mechanical binding in the brake pedal assembly that prevents the sensor from reaching its full travel during the learn cycle.

How to diagnose and fix it

  1. Verify battery voltage and charge if low, then clear the code and perform the manufacturer's brake pedal position sensor learn procedure.
  2. Inspect the sensor B connector and wiring for damage, corrosion, or loose terminals, and repair as needed.
  3. Check the sensor mounting and brake pedal for mechanical binding or misalignment, and correct any issues.
  4. If the learn procedure fails, test the sensor B signal with a scan tool while slowly pressing the brake pedal to confirm a smooth, linear voltage or percentage change.
  5. Replace the brake pedal position sensor B if it fails the signal test or if the learn procedure cannot be completed.
  6. After replacement, perform the relearn procedure and clear codes, then verify the code does not return during a road test.
  7. If the code persists after sensor replacement and relearn, check for control module software updates or internal faults.

When the sensor is not the culprit

  • A common mistake is replacing the brake pedal position sensor B without first attempting a relearn procedure, which is often all that is needed after a battery replacement or module swap.
  • The code can be set by a weak battery that causes the learn procedure to abort, so always verify battery condition before condemning the sensor.
  • Mechanical binding in the brake pedal pivot or a bent sensor bracket can prevent the sensor from reaching its learn limits, mimicking a failed sensor.
  • Some vehicles require the brake pedal to be cycled fully several times during the learn procedure, and skipping this step will leave the code stored.
  • This code does not always mean the sensor is defective; it can also indicate that the control module lost its learned values due to a software glitch or memory corruption.

Can I keep driving with C05C1?

The vehicle is generally safe to drive because the base brakes remain functional, but avoid relying on advanced brake features such as hill-start assist or adaptive cruise control until the code is repaired. Have the system diagnosed and the sensor relearned promptly to restore full brake system functionality.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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