ChassisC0840
CautionSeverity: Caution - get it checked when you can
Control Module Ignition 0 Unlock, On, and Start Circuit
Key terms: 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 · Control module: a small computer that runs one part of the car
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?
If the code names an airbag or SRS system, the airbag may not deploy in a crash: have it diagnosed promptly. If it names electric power steering, the assist may fail and the steering can become heavy: stop safely if that happens. If it names the brakes or park brake, have it checked before driving when braking feels abnormal. Otherwise ABS and stability control may be disabled: drive carefully, especially in wet conditions, and have it checked soon.
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 6
| Brand | Code | Description | System |
|---|---|---|---|
| Daewoo | C0840 | No description available | Chassis |
| GM | C0840 | No description available | Chassis |
| Holden | C0840 | Control Module Ignition 0 Unlock, On, and Start Circuit Brand | Chassis |
| Opel | C0840 | No description available | Chassis |
| Peugeot | C0840 | No description available | Chassis |
| Saab | C0840 | No description available | 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 1
These 7-character codes are manufacturer-specific variants of C0840 and may be reported by some scan tools.
| Brand | Code | Description | System |
|---|---|---|---|
| Mercedes-Benz | C084000 | ISwStatSubstByUZIgnStat - Faulty Signal Isw_Stat is substituted by the HW-Signal KL15 Brand | Chassis |
6Related codes
Browse Cxxx codes or C084xx codes.