Automatic Transmission Control Module problems of the 2021 GMC Acadia

While driving, error popped up stating steering assist is reduced; drive with caution. Heat was no longer working. Engine temp was reading cold even though vehicle had been running for half hour and temp outside was 65 f. After vehicle was stopped, engine fan ran very loudly for at least 15 minutes. Took vehicle in to have diagnostics ran, and received error p0128 pointing to faulty engine coolant thermostat and sensor. Also received u0401 indicating insufficient data coming from ecm/pcm. I was told that together with u0401 and p0128 together indicate a communication problem between control modules. Check engine light was never on.

Driving out of state. My 2021 Acadia with 41,172 miles. When pushing the gas to go there is slippage when trying to accelerate. My car went automatically into neutral saying transmission and then not start. After a rest period it would start then repeat the same issue. In bumper to bumper traffic on i75. The most terrifying & unsafe place to be at 75 to 80 mph. We happened to be driving up on construction and slow down traffic. When the car stalled. Towed it to a transmission place because of code. They replaced the dtr1 pcm.