P0864 code definition
The P0864 code is a generic powertrain code related to transmission problems, including sensor failures and pressure faults. In this case, the engine control module (ECM) has detected a fault with the traction control module, specifically related to the communication circuit.
Codes related to the P0864 include:
- P0856: Traction Control Input Signal
- P0857: Traction Control Input Signal Range/Performance
- P0858: Traction Control Input Signal Low
- P0859: Traction Control Input Signal High
- P0863: TCM Communication Circuit
- P0865: TCM Communication Circuit Low
- P0866: TCM Communication Circuit High
- P0880: TCM Power Input Signal
- P0881: TCM Power Input Signal Range/Performance
- P0882: TCM Power Input Signal Low
- P0883: TCM Power Input Signal High
- P0884: TCM Power Input Signal Intermittent
What the P0864 code means
The P0864 code only applies to vehicles with an electronic traction control system.
Due to the large number of modules utilized, current vehicle’s with a communication area network (CAN) utilize a communication bus to help the ECM share input and output information with the various modules.
When the vehicle’s ECM has failed to receive input or the correct signals from the traction control module, a P0864 code may be stored. The traction control module communication circuit sends information to the ECM, as well as other related controllers, to help determine proper engine RPM and timing, fuel delivery, and more.
What causes the P0864 code?
Several problems may cause a P0864 code including:
What are the symptoms of the P0864 code?
Symptoms of a P0864 code may include:
- Check engine or warning light may illuminate
- Traction control light may flash or stay illuminated
- Decrease in fuel economy
- Transmission may shift harshly
- Transmission may not shift at all
- Transmission may go into “limp” mode
- Some lack traction may be felt in more slippery road conditions
- Traction control may fail
How does a mechanic diagnose the P0864 code?
A mechanic may use several methods to diagnose a P0864 trouble code, including:
- Utilize an OBD-II scanner to check for a stored P0864 trouble code
- Visually inspect all wiring and connectors for signs of damage or corrosion
- Ensure the traction control module is inactive on the network, and check if any other modules are also inactive
- If multiple modules are offline, the error is related to the CAN bus
- Utilize a specialized scanner (such as an Autohex) to help pinpoint the location of the error
- Use a memory saving device to ensure controllers do not lose their memory during reprogramming
- Test for power and ground and at the traction control module
- Check the traction control module data communication line
Common mistakes when diagnosing the P0864 code
The traction control module may be incorrectly replaced when the root of the problem is a damaged or defective switch or poor electrical connection. It is recommended to visually inspect and fully diagnose all possible causes for a P0864 code prior to replacing the traction control module.
How serious is the P0864 code?
Because a vehicle’s safe driving operation most likely will be impacted due to faults that store a P0864 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.
What repairs can fix the P0864 code?
Several repairs can fix a P0864 trouble code and include:
- Replace or repair damaged wiring and connectors
- Replace damaged or defective traction control switch
- Replace damaged or defective traction control module
- Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear
Additional comments for consideration regarding the P0864 code
Due to the amount of electrical componentry and circuitry related to the transmission control module communication circuit, it is recommended to seek the assistance from a professional. Use of a specialized scanner can help pinpoint the location more easily.
Need help with a P0864 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.
This article originally appeared on YourMechanic.com as P0864 OBD-II Trouble Code: Traction Control Module (TCM) Communication Circuit Range/Performance and was authored by Parker Hill.