P0858 Traction Control Input Signal Low

P0858 points to a low traction control input signal. The traction request or status circuit/data path is below the expected state.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not clear the powertrain code without checking ABS or stability-control codes that explain the low input.

Symptoms of P0858

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0858

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Check traction input voltage or network data, ABS module communication, power feeds, grounds, fuses, and related switch circuits.
Compare module data for traction request, wheel-speed validity, brake input, and torque-reduction command during the fault.
Inspect wiring or network connections that carry the traction signal, especially after ABS, brake, or drivetrain service.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.