ECU lost contact with TCM?

Hello, there is a Technical Service bulletin on the P0401 stored in the TCM which looks to be a failsafe type of code. What code are you getting and which module is it stored in? This TSB has to do with the wiring harness rubbing threw on an A/C line on the back passenger side of the engine compartment. I'll post it for you.
And just wondering if you have gone through all the fuses yet, just to check if any have blown. I remember this TCM being in the worst possible location for water intrusion and corrosion. It looks like the TCM for a CVT is the same location.

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

This is the aftermarket High Speed CAN bus, so the 2 wires (White for CAN HIGH) and (black for CAN LOW) should be a twisted pair because they are communications wires. That will help you to identify them. and these splices S100 and S101 are supposed to be near the Starter motor, another bad location for a wiring harness. But you could measure the voltage right at the CVT module to see if there's anything there. You will most likely only read around 2.5-2.8volts roughly with a multimeter on a can bus because the speed is so fast, the multimeter can only average out the voltage reading.
But we need to know the communications code you're getting, if it's a U1000 in the PCM stating Lost of comms with TCM or if it is this P0401.

https://www.2carpros.com/articles/how-to-use-a-voltmeter