OBD code U0101

The vehicle network cannot communicate correctly with the automatic or automated transmission control module.

Estimated severity

High

Common symptoms

Transmission stuck in one gear or limp mode
Harsh or delayed gear engagement
Gear selector warnings
Vehicle may not move or may not start
Communication failure with the TCM on scanner

Likely causes

TCM fuse, relay or power supply issue
Poor ground at the transmission or module
CAN wiring fault between TCM and other modules
Connector with oil, water or corrosion
TCM internal fault

Recommended checks

1. Check whether the scanner can access the TCM directly.
2. Inspect TCM fuses, power supply and ground.
3. Check connector condition at the gearbox or control module.
4. Inspect CAN wiring around the transmission area for heat, oil or rubbing damage.
5. Check for related U-codes in ABS, engine and body modules.

What does code U0101 mean?

U0101 indicates loss of communication with the transmission control module. On vans with automatic, automated manual or dual-clutch gearboxes, this can affect gear selection, limp mode and drivability. The fault may be caused by power supply, ground, CAN wiring, the TCM connector or the module itself.

Try assisted diagnostics