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P0858 is a diagnostic trouble code (DTC) for "Traction Control Input Signal Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $79.99. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
When the powertrain control module (PCM) detects a problem with the traction control input signal circuit, a P0858 trouble code is stored. The traction control input signal circuit delivers data to the PCM via a signal, which the PCM then uses to calculate how much the engine revolutions per minute (RPMs) are needed, engine timing, and how much fuel is needed for current vehicle traction. The P0858 trouble code only applies to vehicles that have an electronic traction control system. Some related trouble codes include P0856, P0857, P0859, and P0860.
When the PCM, or a related module, doesn't receive input from the traction control module, a P0858 trouble code is stored and the check engine light illuminates. In some models, the traction control light might also illuminate and the transmission will be placed in Limp-in mode.
A defective traction control ON/OFF switch is the most likely culprit behind the storage of a P0858 trouble code. Other causes can include damaged wiring or electrical connectors, corrosion in the sensor connector, and liquids spilled into the traction control switch.
Symptoms of a P0858 trouble code include the traction control system failing to operate, which is most obvious in slippery driving conditions. In addition to the warning lights, drivers can encounter problems when shifting gears and an increase in overall fuel usage while driving.
To properly diagnose a P0858 trouble code, a mechanic needs an advanced scanner, digital volt/ohmmeter, a specialized scanner for testing the Controller Area Network (CAN) Bus harness, and a CAN Bus system wiring diagram. In addition, the mechanic should perform the following when diagnosing:
Mechanics most commonly cite the traction control module as being at fault, when in fact the problem lies with a faulty switch, circuit, or connector. Subsequent replacement of the traction control module does not fix the problem causing the P0858 trouble code and the code returns.
While a P0858 trouble code usually doesn't affect the operation of a vehicle with the code, it can lead to issues with gaining proper traction in slippery conditions. In addition, transmission issues in the form of shifting problems are commonly experienced with this code, as well as a decrease in the overall fuel efficiency of the vehicle.
Fixing a P0858 trouble code requires the mechanic to complete the following repairs:
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