Data Bus Powertrain – Malfunction / No Communication.
Verify the ECM and TCM are receiving proper voltage and have good grounds. p1648-vw
This is a communication error between ECUs, not necessarily a failed sensor. 1. Common Causes Data Bus Powertrain – Malfunction / No Communication
Repairing broken CAN bus wires.
Water entering the TCM enclosure (often located under the carpet on the passenger side in Passats/Audis) causes severe corrosion and communication failure. p1648-vw
If internal module damage is diagnosed. If you can provide: The exact vehicle year and model (e.g., 2004 Passat 1.8T). Any other fault codes (e.g., P1626, ABS codes). If the ABS or Transmission light is on.
Check for accompanying codes like P1626 (missing message from TCM) or ABS/TC-related codes.