P0856 OBD-II Trouble Code: Traction Control Input Signal

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0856 DIAGNOSTIC 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 for $69.99. 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.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$69.99$20.00
Toyota$69.99$20.00
BMW$69.99$20.00
SCHEDULE P0856 DIAGNOSTIC Get a fair and transparent estimate upfront

diagnostic check engine light

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
P0856
OBD-II

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0856 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.5/5

Number of Reviews

4,240

Rating Summary
3,884
174
45
26
111
3,884
174
45
26
111
Jerome

Jerome

21 years of experience
246 reviews
Jerome
21 years of experience
He did a great job
2009 HYUNDAI ACCENT - CHECK ENGINE LIGHT IS ON - ESSEX, MARYLAND
Kenneth

Kenneth

17 years of experience
374 reviews
Kenneth
17 years of experience
Have to say, Kenneth is everything mechanics need to strive for. He seemed extremely knowledgeable on all things car-related, is on-time and what I found the most important, is that he gave detailed recommendations on what steps to take first. I have an old, high-mileage, Navigator with multiple problems. In the interest of saving money and not just throwing parts at it hoping it'll run fine afterwards, he gave specific recommendations on what test to get first to make sure the internal engine is fine before tackling everything else wrong with the car. He schooled me on some car terminology which was helpful as well.
2007 LINCOLN NAVIGATOR - CHECK ENGINE LIGHT IS ON - LOS ANGELES, CALIFORNIA
Vladimir

Vladimir

7 years of experience
214 reviews
Vladimir
7 years of experience
Vladimir explained everything clearly and was easy to work with. He was late for a few minutes but that was cool.
2003 TOYOTA AVALON - CHECK ENGINE LIGHT IS ON - ROSEVILLE, CALIFORNIA
Clifton

Clifton

27 years of experience
189 reviews
Clifton
27 years of experience
Clifton was able to find a problem that many others had missed. Pure Genius!
2002 AUDI A4 QUATTRO - CHECK ENGINE LIGHT IS ON - BOCA RATON, FLORIDA

More related articles

P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
P0359 OBD-II Trouble Code: Ignition Coil I Primary/Secondary Circuit Malfunction
P0359 code definition The P0359 code indicates that a fault has been detected in one of the vehicle’s ignition coils, generally the number 9 coil. This code can also be associated...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.

Related questions

Q: Car won't let me accelerate.

Hello there, A continued oxygen sensor and voltage code is a sign there is still a problem with your 2002 Pontiac Firebird. You did not say if you replaced the oxygen sensor in question or not. I am going to...

Q: Knock sensor 1

Hello there. The knock sensor code can have various causes on your 2004 Chevrolet Silverado. The knock sensor circuit low, bank 1 code is telling us that the knock sensor in bank 1 that it has low circuit voltage. This...

Q: Throttle Position Sensor

Anytime you go to a parts store to get a computer scan for the Check Engine Light you are not getting a diagnosis of the problem but only a code retrieved from the engine control module (ECM) memory. This is...

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