ChassisC0021
SeriousSeverity: Serious - have it checked soon
Brake Booster Performance
Key terms: Boost pressure: extra air pressure made by a turbo or supercharger · ABS: anti-lock braking, which stops the wheels locking · Stability control: helps stop the car skidding · Wheel speed sensor: measures how fast each wheel turns · SAE J2012: the standard generic code list
1What it means in plain English
A chassis system has a fault, usually ABS, traction control or stability control, but some makes use this range for airbags, electric power steering or park brakes.
2Common causes
- Faulty wheel speed sensor
- Damaged sensor ring or wiring
- Faulty ABS module
- Low brake fluid
- Wheel bearing damage
3Can I drive?
Have it checked immediately: brakes or brake assistance may be affected. Do not drive if the pedal feels soft or hard, the car pulls when braking, or the brake warning light is on.
This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.
4Brand data 23
| Brand | Code | Description | System |
|---|---|---|---|
| Ashok Leyland CV | C0021 | Battery Charger. Engagement Status. Sensor A. Too High Temperature Brand | Chassis |
| BAIC Motor | C0021 | Brake Booster Performance Brand | Chassis |
| BMW | C0021 | brake booster, plausibility Brand | Chassis |
| BYD | C0021 | Brake Booster Performance SAE | Chassis |
| Chery | C0021 | Brake Booster Performance Brand | Chassis |
| Daewoo | C0021 | See Service Manual DTC Brand | Chassis |
| DFFS | C0021 | Brake Booster Performance Brand | Chassis |
| DFFX | C0021 | Brake Booster Performance Brand | Chassis |
| DFXK | C0021 | Brake Booster Performance Brand | Chassis |
| EOBD | C0021 | Bromsservoprestanda Brand | Chassis |
| Geely | C0021 | Brake Booster Performance Brand | Chassis |
| GM | C0021 | Brake Booster Performance Brand | Chassis |
| Great Wall | C0021 | Brake Booster Performance Brand | Chassis |
| Hafei | C0021 | Brake Booster Performance Brand | Chassis |
| Holden | C0021 | Brake Booster Performance SAE | Chassis |
| Hyundai | C0021 | Brake Booster Performance SAE | Chassis |
| Land Rover | C0021 | Brake booster performance Brand | Chassis |
| Opel | C0021 | Brake Booster Performance Brand | Chassis |
| Peugeot | C0021 | Brake Booster Performance SAE | Chassis |
| Saab | C0021 | Brake Booster Performance Brand | Chassis |
| MG (SAIC) | C0021 | Brake Booster Performance Brand | Chassis |
| Subaru | C0021 | FR Sensor Power Supply Failure Brand | Chassis |
| Toyota | C0021 | Brake booster performance Brand | Chassis |
Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.
5Extended variant codes 9
These 7-character codes are manufacturer-specific variants of C0021 and may be reported by some scan tools.
| Brand | Code | Description | System |
|---|---|---|---|
| Mercedes-Benz | C002100 | OBD relevant DTC in RBS. For detailed information read Fault Memory of RBS Brand | Chassis |
| Mercedes-Benz | C002116 | The brake booster has a malfunction. The limit value for electrical voltage has not been attained. Brand | Chassis |
| Mercedes-Benz | C002146 | The brake booster has a malfunction. There is an error in the calibration or parameterization memory. Brand | Chassis |
| Mercedes-Benz | C002148 | The brake booster has a malfunction. There is an error in the control memory. Brand | Chassis |
| Mercedes-Benz | C002155 | The brake booster has a malfunction. The component is not configured. Brand | Chassis |
| Mercedes-Benz | C002174 | The brake booster has a malfunction. The actuator slips. Brand | Chassis |
| Mercedes-Benz | C0021FA | The brake booster has a malfunction. Brand | Chassis |
| Mercedes-Benz | C0021FB | The brake booster has a malfunction. Brand | Chassis |
| Mercedes-Benz | C0021FC | The brake booster has a malfunction. Brand | Chassis |
6Related codes
Browse Cxxx codes or C002xx codes.