Skip the auto shop - Our mechanics make house calls

P0859 OBD-II Trouble Code: Traction Control Input Signal High

Check Engine Light

P0859 code definition

A P0859 trouble code indicates that the vehicle's Powertrain Control Module (PCM) has reported a malfunction relating to the traction control input signal circuit.

What the P0859 code means

The traction control system regulates several aspects of the vehicle's drive system, particularly with regards to engine power and fuel delivery. A P0859 trouble code will be logged on the vehicle's computer if the PCM fails to receive a signal from the traction control system.

What causes the P0859 code?

  • In the vast majority of cases, the P0859 code is caused by a defective traction control switch. The switch itself may be faulty or damaged. Technicians report defective switches in this code instance are often damaged due to liquid contact.

  • Shorted, corroded and damaged wires may also be to blame for a P0859 signal malfunction. Moreover, technicians have cited a corroded sensor connector as a common reason for this trouble code.

What are the symptoms of the P0859 code?

The reported symptoms of a P0859 code vary from purely traction-related concerns to a failure of the transmission system. Traction problems are most commonly reported, particularly if a P0859 code-afflicted car is driven on slippery surfaces. Harsh or failed shifting may also come alongside a P0859 code. The P0859 trouble code and dashboard trouble indicator will both be activated for the sake of highlighting and diagnosing the concern.

How does a mechanic diagnose the P0859 code?

A technician may first diagnose the P0859 code by reading it via an OBD-II code reader. Components related to the traction system (particularly the traction control system's activation switch) should be inspected and tested for signs of fault or malfunction. All wires relating to the traction control system should be inspected thoroughly in order to verify any potential signs of corrosion, damage, wear or disconnection. In the case that there is a possible issue with one of the vehicle's control modules, a specialized scanner (such as an Autohex) may be used in order to pinpoint the source of the problem.

Common mistakes when diagnosing the P0859 code

Although a faulty traction control module is sometimes to blame for a P0859 code, it is often mistakenly replaced when the real problem lies with broken electrical circuitry or a faulty switch.

How serious is the P0859 code?

A P0859 trouble code can result in drivability issues for the vehicle. Particularly if the vehicle's typical driving surfaces are slippery, a P0859 code can make the vehicle more dangerous to drive. In addition, an unpredictable transmission system resulting from a P0859 can make driving the vehicle a precarious situation.

What repairs can fix the P0859 code?

Additional comments for consideration regarding the P0859 code

The P0859 trouble code only applies to vehicles with electronic traction control systems. Due to the high amount of circuitry associated with this code and the traction system, it is recommended that these repairs be left to a proper technical specialist.

Need help with a P0859 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

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222...
The Traveler’s Guide to Driving in Malaysia
CraigBurrows / Shutterstock.com Malaysia is a popular destination for many tourists today. The country has amazing sights and attractions that you will want to explore....
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...


Related questions

Q: Why is my car sputtering? 2005 Saturn Ion

Hi there - a car that sputters may have an ignition misfire, or a fuel supply issue causing this behavior. You mentioned the Check Engine Light is on - getting the problem codes is task #1. The problem codes will...

Q: I had a leak in my lower radiator hose so I changed it. Now the car won't start now and the Check Engine Light is on.

Hello, lets start with the basics: since the Check Engine Light is on, what problem codes are set? The codes are your friend - will make diagnosis much easier. Do you have spark at the spark plugs while cranking? If...

Q: What means error fault code p1978

The trouble code you listed is a manufacturer specific code, designated by the P1xxx. I have searched my files and cant find that DTC trouble code. Can you please verify that the code is P1978? However, if you'd like to...