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DTC codes / C05xx · Brakes, steering and suspension / C058C

C058CBrake Booster Motor B Position Sensor Circuit Low

C058C indicates that the brake booster motor position sensor circuit has reported a voltage below the expected range to the control module. The computer sets this code when the sensor signal stays lower than the calibrated minimum for a set period, which can prevent the booster motor from operating correctly.

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
  • A hard brake pedal that requires increased effort to stop the vehicle
  • Reduced or absent power brake assist, especially during the first few pedal applications
  • A whining or humming noise from the brake booster area that may be intermittent or absent
  • Often no symptoms besides the warning light, with normal brake feel in some cases

Common causes, most likely first

  1. A faulty brake booster motor position sensor that has failed or is reading low
  2. Damaged or corroded wiring in the sensor circuit, such as a short to ground or an open circuit
  3. A poor electrical connection at the sensor connector or the control module connector
  4. A defective brake booster motor that is drawing excessive current and affecting sensor readings
  5. A failing control module that is misinterpreting the sensor signal
  6. Contamination or debris on the sensor or its magnetic target, causing an erratic low signal

How to diagnose and fix it

  1. Use a scan tool to retrieve all stored codes and freeze-frame data, then clear the code and test-drive to see if it returns
  2. Visually inspect the brake booster motor position sensor connector and wiring for damage, corrosion, or loose pins
  3. Measure the sensor reference voltage and ground at the connector with a digital multimeter to confirm the circuit integrity
  4. Back-probe the sensor signal wire and compare the voltage to the manufacturer's specification while moving the booster motor through its range
  5. Check the brake booster motor for excessive current draw or mechanical binding that could affect sensor operation
  6. If the sensor signal is out of range, replace the brake booster motor position sensor and clear the code
  7. If the circuit and sensor test good, follow the manufacturer's diagnostic flow to test the control module and repair or replace as needed

Before you replace the brake booster motor

  • A low signal from the position sensor often results from a short to ground in the wiring harness, which is frequently overlooked when technicians jump straight to part replacement.
  • The brake booster motor position sensor is sometimes integrated into the booster assembly, so a failed sensor may require replacing the entire booster on certain vehicles, making proper circuit testing essential.
  • This code can be set by a weak or failing battery if the system voltage drops during cranking, so always verify battery and charging system health before condemning the sensor.
  • A brake booster motor that is failing mechanically can cause the position sensor to read low due to abnormal motor operation, so testing the motor itself is a critical step that is often skipped.
  • After repairs, the control module may require a calibration or relearn procedure for the brake booster motor position sensor, which is not always documented in aftermarket manuals.

Can I keep driving with C058C?

If the brake pedal feels normal and the warning light is the only symptom, you can drive cautiously to a repair shop, but avoid heavy braking or towing. If the pedal is hard or braking performance is reduced, stop driving and have the vehicle towed to prevent an accident.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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