P0856Traction Control Input Signal
- Generic OBD-II code · Powertrain
- How the car detects it
- The traction control input carries the request of the ABS/stability module to the engine module to cut torque when wheels spin. Older cars used a wire with a voltage or duty-cycle signal, hence the low and high variants; today it is a CAN message, where pure loss of communication sets U0121 or U0415 instead. California's OBD rule counts traction control as a safety-only system that may be exempted, so these codes normally carry no MIL. GM checks the CAN torque request from the brake module: a wrong protection value or rolling count in 6 of 10 messages, or three changes of request type within 200 ms, set it, type C without MIL. On the Saab 9-4X the brake module then switches traction and stability control off for the key cycle and stores C0242.
- What you may notice
- Traction or stability control lamp on, system switched off
- No torque reduction when wheels spin
- Usually no check engine lamp
- C0242 or similar in the brake module
- Likely causes
- LikelyFault in the engine module that prevents torque reduction, often with other engine codes
- PossibleSoftware of engine or brake module, module faulty
- PossibleCAN fault, connector or ground at the brake or engine module
- RareLow supply voltage
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.