I took my 2001 Ram SLT 1500, 4x4 to Missoula, MT this weekend for Christmas. This is a 180 mile trip which takes you over two mountain passes. Anyways, what my problem is, is the truck will turn overdrive off at its own free will, illuminating the O/D off light. It does not turn back on by pushing the button, in fact, it turns back on randomly, but usually after a few miles or slowing down to a very slow speed. The first time this happened was a few weeks before my trip, with cruise on, at exactly 75mph on flat ground. It turned back on once I got off the freeway and parked, then never did it again until this trip. During the trip, the first time it happened was right when i got to the top of the first pass, going down hill, cruise off, and at about 70mph. It turned back on at the bottom of the pass. Second time happened a few miles later on flat ground, with cruise on, dead on 75mph. Today on my trip back to Washington I never once used cruise, and still did it, a total of 3 times through the drive back, mostly on flat highway.
So it seems that it happens at 70+ mph, cruise does not make a difference, and terrain does not make a difference. I've researched a little since I got back to town tonight, and it seems that a sticky O/D solenoid is common on these 1500's? I know there are a few other components relating to the overdrive, but I dont know my way around a transmission that well. From pictures I've seen it looks like i'd have to pull the transmission? Does anyone know what i'm talking about, had the same problem, or any advice? I should also mention, I do have the P0601 code for the bad PCM. Do you think this could be relating to the overdrive faulting out? I'm a little nervous here because I just bought this truck 3 months ago for $8000 and I really have no extra money for any sort of repairs (hence why i've yet to replace the PCM).