C0021: The brake booster gives readings outside the normal range
The brake booster gives readings outside the normal range. It is usually the part, its wiring or a connector with poor contact.
| Code | C0021 |
|---|---|
| System | Chassis |
| Group | C00xx, Chassis |
| Type | Generic: it means the same on every make |
How to read and clear C0021 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see C0021 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- C001C There is a fault in the rear right intake control
- C001D There is a fault in the rear right output control
- C001E The right rear brake hydraulic pressure takes too long to release
- C0020 There is a fault in the ABS pump motor control
- C0022 The brake booster solenoid is not working properly
- C0023 There is a fault in the stop light control
- C0024 The brake pedal feedback pressure solenoid has an electrical fault
- C0025 The brake pedal feedback pressure sensor has an electrical fault
What does code C0021 mean?
The brake booster gives readings outside the normal range. It is usually the part, its wiring or a connector with poor contact.
How do you clear C0021?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, C0021 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
