Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. P0858 OBD-II Trouble Code: Traction Control Input Signal Low

P0858 OBD-II Trouble Code: Traction Control Input Signal Low

diagnostic check engine light

P0858 code definition

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.

What the P0858 code means

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.

What causes the P0858 code?

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.

What are the symptoms of the P0858 code?

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.

How does a mechanic diagnose the P0858 code?

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:

  • Inspect the wiring, connectors, and components. In particular, look for faulty, corroded, or damaged items during inspection.
  • Download any stored trouble codes or freeze frame data.
  • Install a memory-saving device and test the pins of the CAN Bus harness for wiring for fault using a specialized CAN Bus scanner. The mechanic should keep in mind that this process is time consuming and cost prohibitive.
  • Using a digital volt/ohmmeter, check the CAN Bus circuits, control modules, connectors, and fuses for fault.
  • When checking these components, connectors, and wiring, make sure to test for reference voltage and continuity with the battery ground.
  • Using the volt/ohmmeter, check the continuity and ground at the traction control ON/OFF switch.
  • Clear and retest the system to see if the problem returns.

Common mistakes when diagnosing the P0858 code

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.

How serious is the P0858 code?

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.

What repairs can fix the P0858 code?

Fixing a P0858 trouble code requires the mechanic to complete the following repairs:

Need help with a P0858 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Find the Keyless Code on a Ford Explorer or Mercury Mountaineer
Many Ford Explorers and Mercury Mountaineers were manufactured with an option known as the Ford keyless entry keypad. Some models refer to it as SecuriCode as well. It...
P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...


Related questions

Q: Code p0101

The P0101 trouble code may keep returning if the engine computer does not see the MAF sensor input within a specified range when it is testing the MAF input. The input can be wrong if the engine has another problem...

Q: I have a 2000 dodge ram 2500 and it wont shift gears so I plugged in my code reader to see if it would pull up anycodes vut no pwr

Often, this is caused by a blown fuse in the battery power circuit of the OBD port. It is pin #16 that is B+ on all modern vehicles, such as yours. It appears as though this is fuse #12 on...

Q: o2 sensor reads 0 volts.

You may need to look at the code P0122 since it pertains to the throttle position sensor and this can affect all the drive symptoms you are having. The O2 sensor readings seem to be normal and you are not...