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ENRUDEPLES

U0101 — Lost Communication With Transmission Control Module (TCM)

serious

What it means

The engine module or the gateway no longer sees CAN messages from the transmission control module. Because engine and gearbox coordinate torque reduction during shifts over the bus, that coordination stops and the transmission falls back to its hydraulic default: usually one fixed gear, no lockup and no kickdown. The gear display in the cluster often goes blank or shows dashes.

Likely causes (most common first)

  1. Loss of power or ground supply to the transmission control module
  2. Broken CAN wiring or a corroded connector on the gearbox branch of the bus
  3. Water in the transmission connector or in the module housing
  4. Blown fuse in the transmission control circuit
  5. Internal failure of the transmission control module
  6. Faulty gateway module or bus terminating resistor

Can you drive with it?

You can crawl to a workshop in the emergency gear, but there is no kickdown and no shifting, so keep the speed low.

This is the generic meaning. What about your car?

The same code has different typical culprits on different engines. Tell the AI your make, model and year — it will rank the causes for your exact car and give you a check order.

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