U0101 Lost communication with the transmission control module
- System
- Network - modules not talking to each other
What U0101 means
Modules on the car's shared network send each other regular messages, and the name "Lost communication with the transmission control module" says the ones carrying that module's data stopped arriving. What was measured is whether the expected message showed up in the time it was due; nothing was read from inside the gearbox itself. That is why it sits on the network side as a U code rather than in the P07xx transmission range.
This is a standard code. It means the same thing on every make of vehicle.
What the program shows for U0101
Nothing on the program's list of readings comes from the module this code names: the closest are the Dashboard's Engine speed and Vehicle speed gauges, and both are figures the engine computer reports. The freeze frame tab, When it happened, is the same story - it only ever lists gauges from the program's own list, all of them engine readings.
The Trouble Codes screen names the module the car lost contact with, from the engine and transmission modules to ABS, body, restraints and the instrument cluster, where the module is on its list. Look up a code does the same offline and says whether a code is standard or manufacturer-specific, and the Adapter traffic screen shows the raw requests and replies. Compare between two recordings shows whether the code is Gone, New or Still there.
See how the program shows a code →