OBD Guide

C05B9

Brake Booster Motor A Position Sensor Supply Circuit Low

C05B9 is an OBD-II diagnostic trouble code meaning: Brake Booster Motor A Position Sensor Supply Circuit Low. Common causes: open or short circuit in the sensor wiring harness, brake booster motor position sensor malfunction. Estimated repair cost: $56–167.

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

Symptoms

  • Increased brake pedal force
  • The brake system fault indicator lights up
  • Reduced braking performance

Causes

  • Open or short circuit in the sensor wiring harness
  • Brake booster motor position sensor malfunction
  • Problems with power or grounding of the circuit
  • Malfunction of the brake control unit (ECU)

How to Fix

  1. Check the wiring harness for damage or corrosion.
  2. Measure the voltage in the sensor power circuit
  3. Check the resistance of the position sensor
  4. If necessary, replace the sensor or wiring harness
  5. Check and, if necessary, replace the brake system control unit

Related codes

Error C05B9 by Vehicle Brand

FAQ

What does the C05B9 code mean?

C05B9 is an OBD-II diagnostic trouble code that indicates: Brake Booster Motor A Position Sensor Supply Circuit Low

What causes a C05B9 error code?

The most common causes of C05B9 include: Open or short circuit in the sensor wiring harness; Brake booster motor position sensor malfunction; Problems with power or grounding of the circuit; Malfunction of the brake control unit (ECU).

How do I fix a C05B9 diagnostic trouble code?

To fix C05B9: Check the wiring harness for damage or corrosion.. Measure the voltage in the sensor power circuit. Check the resistance of the position sensor. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C05B9?

Limited driving only, diagnose soon

How much does it cost to fix C05B9?

The estimated repair cost for C05B9 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

See also: Russian version · NationStat