Damaged or chafed wiring in the traction control input signal circuit, causing a short to ground; Corroded or loose electrical connector at the traction control switch, ABS module, or PCM; Failed traction control input switch or button stuck in the engaged position; Faulty ABS control module not sending the correct signal to the PCM; Internal short in the PCM input circuit; Poor ground connection for the traction control system or ABS module

DTC codes / P08xx · Transmission / P0858

P0858Traction Control Input Signal Low

Q: What does code P0858 mean?

Traction Control Input Signal Low. P0858 means the powertrain control module (PCM) has detected a low voltage on the traction control input signal circuit, indicating the signal is below the expected threshold or shorted to ground. The PCM monitors this input to coordinate traction control interventions with the anti-lock brake system (ABS) and engine torque management, and it sets the code when the signal remains outside the valid range for a calibrated time.

P0858 means the powertrain control module (PCM) has detected a low voltage on the traction control input signal circuit, indicating the signal is below the expected threshold or shorted to ground. The PCM monitors this input to coordinate traction control interventions with the anti-lock brake system (ABS) and engine torque management, and it sets the code when the signal remains outside the valid range for a calibrated time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaTransmission

Symptoms you may notice

Traction control warning light illuminated on the dashboard
Traction control system disabled, often accompanied by an ABS light
Reduced engine power or limp mode in some vehicles
Intermittent activation of the traction control system without wheel slip
Often no symptoms besides the warning light

Common causes, most likely first

Damaged or chafed wiring in the traction control input signal circuit, causing a short to ground
Corroded or loose electrical connector at the traction control switch, ABS module, or PCM
Failed traction control input switch or button stuck in the engaged position
Faulty ABS control module not sending the correct signal to the PCM
Internal short in the PCM input circuit
Poor ground connection for the traction control system or ABS module

How to diagnose and fix it

Inspect the traction control switch and related connectors for physical damage, corrosion, or loose pins
Check the traction control input signal circuit for continuity to ground with a multimeter; repair any shorted wiring
Verify the ground connections for the ABS module and traction control system are clean and tight
Test the traction control switch operation with a scan tool to confirm it toggles the signal correctly
Substitute a known-good ABS control module if the signal circuit tests normal but the code persists
Check for technical service bulletins (TSBs) or software updates for the PCM or ABS module that address this code
If all external circuits and components test good, diagnose the PCM for an internal fault

Before you replace the ABS module

A low signal on the traction control input circuit is frequently caused by a chafed wire harness near the steering column or under the dashboard where the switch wiring flexes, not by a failed module.
Some vehicles use a momentary-contact traction control switch that sends a pulsed ground signal; a stuck-closed switch will produce a constant low signal and set P0858 without any other symptoms.
The code can be set by a poor ground at the ABS module even when the traction control switch and wiring test perfectly, so always load-test grounds rather than just checking continuity.
P0858 is often misdiagnosed as a faulty PCM when the real problem is a shorted signal wire inside a connector that only shows up when the harness is wiggled, so perform a wiggle test while monitoring live data.
On vehicles with a shared traction control and stability control switch, a failure in the switch can set P0858 alongside codes for the stability system, leading technicians to replace the wrong module.

Can I keep driving with P0858?

You can generally continue driving with P0858 because the vehicle remains controllable, but traction control and possibly stability control will be disabled, so avoid slippery conditions and aggressive driving. If the vehicle enters limp mode or the ABS light is also on, have it inspected promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.