C0105 critical

Brake Booster Pressure Sensor Circuit Malfunction

The C0105 code means the vehicle's onboard diagnostic system has detected: Brake Booster Pressure Sensor Circuit Malfunction. This is a critical severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $100 - $500 (parts and labor)

Read ABS Codes

BlueDriver Bluetooth Pro Scanner

Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.

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Read ABS Codes

LAUNCH CRP123X (Reads ABS + Chassis)

Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.

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Common Symptoms

Hard brake pedal feel
Brake assist not functioning
ABS warning light on
Longer stopping distances
Electronic brake force distribution disabled

Probable Causes (Ranked by Likelihood)

Failed brake booster pressure sensor Very High
Vacuum leak at brake booster hose High
Corroded sensor connector Moderate
ABS module sensor input circuit failure Low

Step-by-Step Diagnostic Procedure

Scan ABS module for booster pressure DTCs
Read booster pressure sensor data with scan tool
Check vacuum hose to brake booster for leaks
Test sensor output voltage under various pedal pressures
Inspect sensor connector for damage

Frequently Asked Questions

What is the brake booster pressure sensor?

It measures the vacuum or hydraulic pressure in the brake booster to determine the level of power assist being provided. The ABS module uses this data for brake assist and emergency braking functions.

Can I drive with a hard brake pedal?

Only for short distances and at low speeds. A hard pedal means reduced power assist, requiring much more effort to stop. Stopping distances will be significantly longer.

Is this related to the brake booster itself?

The sensor measures booster performance, but a failed sensor does not mean the booster has failed. However, if the booster itself has a vacuum leak, it can also trigger this code.