OBD-II code · Network
U0101 Lost Communication with TCM
The ECU has stopped receiving messages from the transmission control module. The transmission falls into limp-home mode (typically locked in 3rd or 4th gear), the speedometer may stop working, and shift adaptation freezes.
Is it safe to drive with U0101?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyTCM unpowered or grounded poorly
- PossibleCAN wiring to TCM broken
- Less likelyGateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–8 h
- Emissions test
- Usually unaffected
- Parts involved
- Tcm, Can Bus Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.