P0864Generic code

P0864 Code: TCM Communication Circuit Range/Performance

The P0864 code means the communication with the transmission control module (TCM) is out of its expected range or performance. The transmission may go into limp mode, or the shifter may stop responding. Damaged wiring or a module without power is the usual cause.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$20 to $900
Difficulty
Medium
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

On this page

What the P0864 code means

Some vehicles have a dedicated communication line to the transmission control module, in addition to the general CAN network. The shifter position, the shift commands and the transmission status travel over it.

The P0864 code is stored when that communication is present but does not behave as expected. The transmission then does not receive or send essential information reliably and activates limp mode. Check power and ground at both modules and the wiring between them. If other U codes are stored, resolve them first.

Always start with the simplest things: fuse, relay and connector. Then check power, ground and signal with the component plugged in (using back-probes), and finally the continuity of each wire to the computer. Only replace a module when everything else checks out.

P0864 code symptoms

  • Transmission in limp mode.
  • The shifter does not respond or the gear indicator does not work.
  • Check engine light on.

Likely causes of the P0864 code

  1. Damaged communication wiring, either cut or shorted.
  2. Power or ground problem at one of the modules. A module with no power cannot communicate.
  3. Corroded connector, which raises the resistance of the line.
  4. Shifter module or transmission module with an internal fault.

How to diagnose the P0864 code step by step

  1. Check power and ground at both modules.
  2. Test the communication line for continuity and for the absence of shorts.
  3. Read related U codes.

How to fix the P0864 code

  • Repair the wiring or the connector.
  • Replace the faulty module.

Technical reference data

  • Dedicated communication line or CAN network, depending on the vehicle.
  • Reference values are only a guide, so look up the manufacturer data for your vehicle.

Brand-specific notes

On vehicles with an electronic shifter, the shifter module is the first suspect when you see a P0864 code.

P0864 on BMW

On BMW vehicles with an electronic shifter, the shifter module is the first suspect.

P0864 on Mercedes

On Mercedes vehicles with an electronic shifter, the shifter module is the first suspect.

P0864 on Jeep

On Jeep vehicles with an electronic shifter, the shifter module is the first suspect.

P0864 on Ford

On Ford vehicles with an electronic shifter, the shifter module is the first suspect.

Frequently asked questions about P0864

Can I drive with a P0864 code?
With caution. The transmission may go into limp mode, and the shifter may not respond, so get it checked soon.
What usually fails?
The wiring or one of the modules.
Does a new module need to be programmed?
Many times, yes.
How much does it cost to fix P0864?
Between $20 and $900, from a simple wiring repair up to replacing a module.
What does the P0864 code mean?
It is a generic OBD2 code that means the TCM communication circuit is outside its expected range or performance.

Related codes

Questions about the P0864 code

There are no questions about this code yet. Tell us about your case: vehicle, symptoms and what you have already checked.