Fault codeP0859

MODERATE

Traction Control Input Signal High

What this code means

Traction Control Input Signal High.

P0859 is a generic code: it means the same thing on every make. P0859 belongs to family P08xx — Transmission (continued). Its page explains how to read a code and groups all its codes by part.

Type of fault

The control unit reads a voltage on this circuit above its expected range. Usual causes: a broken wire or a poor ground, a short to a supply voltage, or the component itself. As with a low signal, check the wiring and connector before the part.

Traction control signal

The traction control unit, part of the ABS/ESP system, asks the engine control unit to cut torque when a wheel slips. These codes concern the signal between the two.

What you notice

Traction control or ESP warnings, power that drops unexpectedly or a system that does not intervene.

How to check it

Read the codes of the ABS/ESP unit too: the source of the fault is often there, such as a wheel speed sensor. Then check the communication wiring between the modules.

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
8Transmission (continued)
59P0859