P0858Traction Control Input Signal Low
- 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. P0858 means a wired signal stays below its lower limit: short to ground, an open line without pull-up, or a sending module without power. No maker documents the code; the request is discarded and traction control switched off.
- What you may notice
- Traction or stability control lamp on, system switched off
- No torque reduction when wheels spin
- Likely causes
- LikelySignal wire from brake module to engine module shorted to ground
- PossibleOpen circuit or connector fault
- PossibleBrake module without power or ground, or faulty
- RareInput of the engine module faulty
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.