I bought a 2000 S40, which now has 135,000 miles. I pulled code TCM-0054 with no description, and can't get any OBD codes off of it for the trans. After some research I found that the code description is "Lock-up pressure switch". I cleared the code, and had O/D once, then never again on the 15 minute freeway drive home. Only dropped out of O/D because I stopped to turn on to the freeway. Has anybody else had this problem? I'm really hoping the trans doesn't need to come out. I already have almost as much as I bought the car for dumped into repairs.

 

Sounds like you need to replace the switch. I'd bet money it can be repaired in the car.