P0856 OBD-II Trouble Code: Traction Control Input Signal

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0856 code

P0856 is a diagnostic trouble code (DTC) for "Traction Control Input Signal". 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. 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.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0856 DIAGNOSTIC Get a fair and transparent estimate upfront

P0856 code definition

The P0856 trouble code detects an issue with the traction control input signal.

What the P0856 code means

The P0856 code is a standard OBD-II trouble code that notes a problem with the traction control input signal. The traction control input signal is responsible for sending data to the powertrain control module (PCM), and other control modules. The PCM and the other control modules use this data to determine the proper revolutions per minute (RPM) for the vehicle, as well as engine timing, fuel delivery, and many other factors. When the PCM and accompanying control modules do not get input signals from the traction control module, then the P0856 trouble code will be triggered.

What causes the P0856 code?

The P0856 trouble code is usually caused by a faulty ON/OFF switch in the traction control system. This usually is the result of spills or leakage damaging the control switch, or faulty, loose, or damaged wires, connectors, and other electrical components in the system. In addition to a defective switch, corrosion on the traction control sensor connector can cause the P0856 code to be detected. While it is rare, the traction control module may also be defective.

What are the symptoms of the P0856 code?

When the P0856 trouble code is detected, the check engine soon warning light will illuminate on the instrument cluster, and the traction control malfunction warning light will likely illuminate as well. In addition to these warnings, the traction control system is likely to stop working, which can result in a loss of grip (mainly on slippery or icy conditions). The transmission may also have a hard time shifting, or may not shift at all (and may enter limp-in mode), and the vehicle will likely experience reduced fuel economy.

How does a mechanic diagnose the P0856 code?

The P0856 code should be diagnosed using a standard OBD-II trouble code scanner. A trained mechanic will use the scanner to view the freeze frame data, and assess the code. The mechanic will also look for the presence of additional trouble codes. The codes should then be reset, and the vehicle should be restarted, to see if the code persists. If the code does not return, then it was likely triggered erroneously, or represents an intermittent issue.

If the P0856 trouble code returns, the mechanic should visually inspect the electrical components in the traction control system, to see if there are any loose, damaged, or corroded wires and connectors. All damaged components should be replaced. If the technician notices that the ON/OFF switch is damaged as well, it should be replaced.

Every time a component is replaced, the codes should be reset and the vehicle restarted before the mechanic proceeds. This will allow the mechanic to tell whether the issue has been resolved, or if there is more work to do.

Common mistakes when diagnosing the P0856 code

The most common mistake made when diagnosing the P0856 code is the failure to adhere to the OBD-II trouble code diagnosis protocol. All mechanics should follow the protocol properly, to ensure that both the diagnosis and the repair is not only properly done, but efficient as well.

It is common for the traction control module to be replaced when the only issue was a faulty ON/OFF switch or some damaged electrical components.

How serious is the P0856 code?

A vehicle with the P0856 trouble code present is still drivable. However, the vehicle’s traction control system will likely be disabled, meaning the car will not have good traction on wet or icy roads. Furthermore, unnecessary stress may be placed on the transmission, which can ultimately cause damage. Even though the car may be drivable, the P0856 code should be inspected and resolved as quickly as possible.

What repairs can fix the P0856 code?

Some possible repairs for the P0856 trouble code include:

Additional comments for consideration regarding the P0856 code

The P0856 trouble code only applies to cars that have electronic traction control systems.

Need help with a P0856 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.

trouble codes
OBD-II
P0856

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0856 code.

SCHEDULE P0856 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,010

Rating Summary
4,615
191
48
28
128
4,615
191
48
28
128

Kenneth

19 years of experience
509 reviews
Kenneth
19 years of experience
Toyota Sequoia - Check Engine Light is on - Newport Beach, California
Kenneth did a great job and very knowledgeable. He has a great attitude and I will for sure be using him again.

Richard

11 years of experience
45 reviews
Richard
11 years of experience
Honda Civic - Check Engine Light is on - Tucson, Arizona
Had damage to wires leading to a coil and was unable to drive the car to a service center so I took a chance on having somebody come out to work on the car. It couldn't of worked out any better. Would definitely recommend Richard to anybody needing car service.

Clifton

29 years of experience
207 reviews
Clifton
29 years of experience
Dodge Ram 1500 - Check Engine Light is on - Lake Worth, Florida
Clifton was on time and very professional. I will definitely recommend him to my friends and family.

Walter

45 years of experience
85 reviews
Walter
45 years of experience
Nissan Sentra - Check Engine Light is on - Tulsa, Oklahoma
Very helpful and knowledgeable. Appreciate the friendliness on top of it, would definitely recommend.


More related articles

B1903 OBD-II Trouble Code: Air Bag Crash Sensor #1 Ground Circuit Short to Battery
B1903 means there is a problem with the ground circuit for the air bag crash sensor #1, likely due to damaged electrical components or a bad sensor.
B1983 OBD-II Trouble Code: Driver's Door Unlock Relay Circuit Short to Battery
B1983 means there is a short circuit issue in the driver's door unlock relay. This is likely due to a faulty electrical component.
P0510 OBD-II Trouble Code: P0510 Closed Throttle Position Switch Malfunction
P0510 means a problem with the vehicle's throttle plate. Some issues are frequent engine stalling, high or low engine idling and trouble accelerating.

Related questions

What does electrical exhaust pressure valve do and code says it's permanent

From the information I can gather on this trouble code, it looks like it is more of a general information code. There is a diagnostic flow chart that needs to be followed to identify if it is a problem with...

KOEO test code 332

Hello there, A few different things can cause insufficient EGR flow. The most likely are: a stuck closed EGR valve a failed EGR valve solenoid faulty oxygen sensor low fuel pressure exhaust leak These can also...

The truck starts then stalls or shuts off

This could be a wide variety of potential issues ranging from a vacuum leak, bad idle air control valve, low fuel pressure, bad coil packs, or many other possibilities. When this happens you should have a Check Engine Light on...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com