U0101Network
CAN network · SAE
Lost Communication With Transmission Module (TCM)
Meaning
The ECU has lost communication over the data network with the transmission control module (TCM). The modules can no longer exchange the messages needed to coordinate engine and transmission.
Common causes
- CAN network wiring broken or shorted
- Corroded or loose TCM connector
- Missing TCM power supply or ground
- Faulty transmission module (TCM)
- Network disturbance from another faulty module
Symptoms
- Check engine and often transmission lights on
- Transmission in limp mode (fixed gear)
- Missing or wrong shifts
- Several modules with lost-communication codes
Severity
Serious: without dialogue with the transmission, the gearbox goes to a safe state; diagnose immediately.
What to do
- Check the transmission module's power supply and ground
- Check continuity and resistance of the CAN wires to the TCM
- Inspect connectors for corrosion and loose contacts
- Isolate the disturbing module if several modules are involved