[Blue Bowtie]

My suspicion is a connection somewhere between the PCM and trans round connector. A poor connection may fool the PCM into thinking there is an open (or high resistance) solenoid connected.

You can try removing and reseating (and inspecting while disconnected) the two PCM connectors, but they are usually fairly well sealed. There may be another connector at the bulkhead, and then there is the harness (round) connector at the trans pan flange itself.

There are replacement trans wire harnesses available also, but you probably already know that having been involved in trans work.