C0021
Brake Booster Performance
C0021 is an OBD-II diagnostic trouble code meaning: Brake Booster Performance. Common causes: vacuum leak in amplifier, vacuum hose damage. Estimated repair cost: $56–167.
Symptoms
- Stiff brake pedal
- Increased pedal travel
- Reduced braking performance
- Hissing sound when pressing the brake
Causes
- Vacuum leak in amplifier
- Vacuum hose damage
- Malfunction of the pressure sensor in the amplifier
- Open or shorted wiring harness
- Mechanical damage to the amplifier
How to Fix
- Check the tightness of the vacuum system
- Inspect the vacuum hose and connections
- Check the operation of the pressure sensor
- Test the sensor electrical circuit
- If necessary, replace the brake booster
Related codes
Error C0021 by Vehicle Brand
FAQ
What does the C0021 code mean?
C0021 is an OBD-II diagnostic trouble code that indicates: Brake Booster Performance
What causes a C0021 error code?
The most common causes of C0021 include: Vacuum leak in amplifier; Vacuum hose damage; Malfunction of the pressure sensor in the amplifier; Open or shorted wiring harness.
How do I fix a C0021 diagnostic trouble code?
To fix C0021: Check the tightness of the vacuum system. Inspect the vacuum hose and connections. Check the operation of the pressure sensor. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with C0021?
Limited driving only, diagnose soon
How much does it cost to fix C0021?
The estimated repair cost for C0021 is $56–167. Actual cost depends on your vehicle, location, and labor rates.
See also: Russian version · NationStat