Parts
$0-800+
U0101 — Lost Communication With TCM
STOPIs it safe to drive? The engine computer lost contact with the transmission control module. The transmission will likely go into limp mode — don't drive this until the cause is found.
What U0101 means
This is a network code, not a transmission fault: the TCM stopped responding on the CAN bus. Before assuming the TCM is bad, check its fuses, power supply, and grounds — those fail far more often than the module itself. A CAN bus fault also triggers this.
Most likely causes (in order)
- Blown TCM fuse or lost power/ground to the TCM
- CAN bus wiring fault between the TCM and gateway
- Corroded or damaged TCM connector
- Failed TCM (less common than power/ground issues)
Symptoms you might notice
- Transmission stuck in limp mode
- No communication with TCM on scan tool
- Multiple trans codes set
What to check first
Pull the TCM fuses and check them. Verify power and ground at the TCM connector with the key on. If power/ground are good and you can't communicate with the TCM, check CAN-H/CAN-L continuity to the gateway before replacing the module.
Repair cost & difficulty
Labor
0.5-6 hr
Difficulty
DIY-friendly