Traction Control Input Signal Low
The P0858 code means the vehicle's onboard diagnostic system has detected: Traction Control Input Signal Low. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $800 (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.
Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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Common Symptoms
- Check Engine Light illuminated
- Traction control system disabled
- TCM does not receive traction control commands
- Stability control warning light on
Probable Causes (Ranked by Likelihood)
- Short to ground in traction control signal wire to TCM Very High
- Faulty ABS/traction control module output High
- Corroded wiring connector in signal path Moderate
- TCM input circuit pulled low Low
Frequently Asked Questions
What happens if the traction control signal stays low?
The TCM will not receive traction control commands and will not reduce torque during wheel slip events. The vehicle can still be driven but with reduced stability assistance.
Is P0858 related to the ABS system?
Yes, traction control is a function of the ABS system. The ABS module sends traction control data to the TCM, so ABS faults can trigger transmission-related codes.
Can I just disconnect the traction control?
Disabling traction control is not recommended as it reduces vehicle safety. The underlying electrical fault should be repaired.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Measure voltage on the traction control signal wire at the TCM connector
-
Check for short to ground in the wiring between ABS module and TCM
-
Inspect connectors at both modules for corrosion
-
Verify ABS module output using a bidirectional scan tool
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- 2008-2018 Honda Accord
- 2010-2020 Hyundai Sonata
- 2007-2017 Nissan Altima
- 2009-2019 Kia Optima
Related Codes
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