C0021

Brake Booster Performance

Severity

🔴 High

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$56–167 (est.)

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

C0020 C0022 P0571