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.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Traction or stability control lamp on, system switched off
- No torque reduction when wheels spin
Most likely causes
- Signal wire from brake module to engine module shorted to ground
- Open circuit or connector fault
- Brake module without power or ground, or faulty
- Input of the engine module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0858 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 8: Transmission
- 58: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0858?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P0858?
The most common causes are: signal wire from brake module to engine module shorted to ground; open circuit or connector fault; brake module without power or ground, or faulty.
Related codes
- P0856Traction Control Input Signal
- P0857Traction Control Input Signal Range/Performance
- P0859Traction Control Input Signal High
- U0121Lost Communication with ABS Control Module
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- saabwisonline.com: dtc c0242 or p0856
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.