P0864
TCM Communication Circuit Range/Performance
- Severity
- High
- Driving
- Drive only to a garage
The transmission module is communicating, but the messages are not what the receiving module expects - corrupted, incomplete, or carrying implausible values. The link works; what travels over it is wrong. This often follows a module replacement that was never coded to the vehicle, or a software mismatch between modules.
Possible causes
- CommonModule replaced but not coded or configured to the vehicle
- CommonSoftware version mismatch between modules after a partial update
- CommonBus wiring damage corrupting messages
- CommonLow battery voltage causing erratic behaviour
- PossibleFailed module
- PossibleAftermarket device injecting traffic onto the bus
What you might notice
- Transmission stuck in one gear
- Erratic shifting
- Warning lights across several systems
- Gear display wrong
- Check engine light on
What to check, in order
- Ask whether any module has been replaced or updated recently. Coding and software mismatches are the leading cause of this code, and no amount of wiring diagnosis will find them.
- Check battery voltage and state of charge.
- Check the software versions of the modules involved if the tool can read them.
- Inspect the bus wiring and connectors for damage.
- Ask whether an aftermarket tracker, dashcam or performance device has been connected to the diagnostic socket or the bus.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Transmission
P0800P0801P0802P0803P0804P0805P0806P0807P0808P0809P0810P0811P0812P0813P0814P0815P0816P0817P0818P0819P0820P0821P0822P0823P0824P0825P0826P0827P0828P0829P0830P0831P0832P0833P0834P0835P0836P0837P0838P0839P0840P0841P0842P0843P0844P0845P0846P0847P0848P0849P0850P0851P0852P0853P0854P0855P0856P0857P0858P0859P0860P0861P0862P0863P0864P0865P0866P0867P0868P0869P0870P0871P0872P0873P0874P0875P0876P0877P0878P0879P0880P0881P0882P0883P0884P0885P0886P0887P0888P0889P0890P0891P0892P0893P0894P0895P0896P0897P0898P0899