Traction Control Input Signal
The P0859 code means the vehicle's onboard diagnostic system has detected: Traction Control Input Signal. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $600 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
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Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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Common Symptoms
- Check Engine Light on
- Traction control warning light on
- Traction control system disabled
- Transmission may not respond to traction events
Probable Causes (Ranked by Likelihood)
- Faulty traction control input signal to TCM Very High
- Communication failure between ABS module and TCM High
- Wheel speed sensor providing incorrect data Moderate
- TCM traction control input circuit failure Low
Step-by-Step Diagnostic Procedure
-
Check for additional ABS or wheel speed sensor codes that may be the root cause
-
Verify all four wheel speed sensors are reading correctly using a scan tool
-
Inspect the wiring between the ABS module and TCM for damage
-
Check the CAN bus communication between modules for errors
Frequently Asked Questions
What is the traction control input signal?
The TCM receives traction control input from the ABS/stability control module. When wheel slip is detected, the TCM can reduce engine torque or modify shift strategy to regain traction.
Can a wheel speed sensor cause P0859?
Yes. The traction control system relies on wheel speed sensor data. A faulty sensor can send incorrect data that the ABS module relays to the TCM, triggering P0859.
Is it safe to drive without traction control?
You can drive without traction control, but use extra caution on wet, icy, or loose surfaces. The vehicle will not automatically reduce power or apply brakes to correct wheel spin, so you must manage traction manually.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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