Fault-Code Library · Network communication
U0101: Lost communication with transmission control module
Other control modules cannot communicate reliably with the transmission controller.
Common symptoms
- •Transmission warning
- •Limp mode
- •No gear display
- •No-start on some vehicles
Likely causes
- •Low system voltage
- •TCM power or ground loss
- •CAN wiring fault
- •Mechatronics or module failure
First checks
- •Test battery voltage
- •Scan all modules for a network pattern
- •Check TCM powers, grounds, fuses, and CAN integrity
Important
Prove power supply and network integrity before replacing or programming a transmission controller.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
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