Damaged or corroded wiring in the TCM communication circuit (CAN high/low or serial data lines); Poor electrical connections at the TCM, PCM, or other network modules; Faulty TCM or internal communication driver failure; Failed or failing transmission range sensor (TRS) or internal mode switch affecting signal integrity; Electromagnetic interference (EMI) from aftermarket accessories or faulty ignition components; Low battery voltage or poor grounds causing communication errors; Software or calibration issues in the TCM requiring reprogramming

DTC codes / P08xx · Transmission / P0864

P0864TCM Communication Circuit Range/Performance

Q: What does code P0864 mean?

TCM Communication Circuit Range/Performance. P0864 indicates that the transmission control module (TCM) has detected a communication circuit range or performance fault, typically on the controller area network (CAN) bus or a dedicated serial link between the TCM and other modules. The TCM sets this code when the signal voltage, message timing, or data integrity falls outside the expected range, often due to wiring issues, module faults, or network interference.

P0864 indicates that the transmission control module (TCM) has detected a communication circuit range or performance fault, typically on the controller area network (CAN) bus or a dedicated serial link between the TCM and other modules. The TCM sets this code when the signal voltage, message timing, or data integrity falls outside the expected range, often due to wiring issues, module faults, or network interference.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaTransmission

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or transmission warning light
Often no symptoms besides the warning light, especially if communication is intermittent
Harsh or erratic shifting, or the transmission entering limp mode
Failure of the scan tool to communicate with the TCM
Multiple unrelated warning lights or module communication codes
Intermittent stalling or no-start if the TCM is part of the immobilizer or gateway network

Common causes, most likely first

Damaged or corroded wiring in the TCM communication circuit (CAN high/low or serial data lines)
Poor electrical connections at the TCM, PCM, or other network modules
Faulty TCM or internal communication driver failure
Failed or failing transmission range sensor (TRS) or internal mode switch affecting signal integrity
Electromagnetic interference (EMI) from aftermarket accessories or faulty ignition components
Low battery voltage or poor grounds causing communication errors
Software or calibration issues in the TCM requiring reprogramming

How to diagnose and fix it

Perform a battery and charging system test to rule out low voltage as the root cause
Inspect and clean all TCM, PCM, and related module connectors for corrosion or loose pins
Check the communication circuit wiring for continuity, shorts to ground, and shorts to power using a digital multimeter
Use an oscilloscope to verify CAN bus signal integrity and look for distortion or noise
Check for aftermarket accessories wired into the network and disconnect them temporarily
Reprogram or update the TCM software if a known calibration issue exists
Replace the TCM only after all wiring and power/ground checks pass, then perform relearn procedures

Before you replace the transmission control module

A weak or failing battery often causes this code because communication modules require stable voltage to transmit and receive data reliably.
Corroded ground straps or a loose engine-to-body ground can create voltage offsets that mimic a TCM failure, so always verify grounds before condemning the module.
Aftermarket alarms, remote starters, or poorly installed audio equipment can introduce noise onto the CAN bus and set P0864 without any actual TCM fault.
The code can be stored intermittently and may not reappear during a short test drive, so a thorough wiggle test of the harness while monitoring live data is essential.
Some vehicles use a dedicated serial link between the TCM and PCM, and a fault in that link can set P0864 even though the CAN bus itself is healthy.

Can I keep driving with P0864?

If the vehicle drives normally and only the warning light is on, you can drive cautiously to a repair shop, but avoid long trips or heavy loads. If the transmission is in limp mode, shifting harshly, or the engine stalls, stop driving and have the vehicle towed to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.