I have a 2003 2500 RAM with the 5.9 diesel and automatic. Around town I have no issues but when I hook up my 7000 lb trailer and get out on the highway I have this problem.

Tranny shifts up through the gears into 3rd normally...around 50MPH or so, it will go into O/D. It will only stay there for a couple of seconds and drop back into 3rd and the TCC will disengage and re-engage every couple of seconds, sometimes even faster, sometimes so fast it doesn't seem to even completely lock up before it's back out. All this on a flat road, no movement on the throttle. With O/D turned off, the TCC will lock and unlock repeatedly in 3rd...every few seconds for the entire trip.

I've had it checked up the ying yang. The Throttle position sensor has been replaced, the output speed sensor has been replaced. There has been a nice braided ground strap installed from the PCM to the fender. There is a noise suppressor been put on to eliminate potential electrical noise.....no change to the issue. The 5 star dealer says all the sensors check out 'rock-solid......I just got it back from resting at the tranny shop for 3 weeks. They took it out onto the highway with the trailer and scanned it, several times.....apparently the transmission is being commanded to shift this way so they don't feel it's a problem with the tranny.

I connected a toggle switch to the lock-up solenoid where it enters the PCM and once I hit lock up in 3rd, I flipped the switch.....the plan was to keep the solenoid engaged and see it that worked just for diagnostic purposes( I had O/D turned off). All that happened was the lock-up engaged for a coujple of seconds and then the thing went into limp-mode, unlocked, and I had to shut the truck off and start it again to reset.

I have made an appointment to have the PCM flashed to stock just in case but I'm leaning to replacing the PCM....it's about all that's left.

Anyone have any cool ideas or suggestions?

What I'd like in the short term is a way of forcing the thing, once it's shifted into 3rd, to lock up and stay there until I switch it back, so I can take my RV out for the long weekend and not toast the tranny. If anyone can tell me how to put this together I'd appreciate it.. I've already had to miss one long weekend because of this and my wife is getting pretty choked. I told her when I bought the truck that it was going to be the cat's meow for towing the RV......I've got a reputation to maintain and it's getting pretty beat up.

Help.

Rob

 

I have heard issues about dirty battery terminals causing the problem you are describing.

 

It's one of the things among many that has been looked into It's got new batteries and new cables.....no issues there, plus I've put on a fairly expensive electrical noise filter from DTT, plus a steel braided ground strap from the PCM housing to the fender ground point, all to no avail.

As one of the TPS adjusting posts on this site advised, I tried to adjust the TPS from its setting of .59 volts at idle up to 1.2 volts. Without knocking out the steel inserts I was able to get it to .7 volts. I figured I'd see what that does before I went any further......all I got to show for my effort was the MIL is now on..........

I found an article from Chrysler (C42 - customer satisfaction?) which advised that there was a kit available to correct water getting into the PCM via the 32 PIN connectors. According to the article, O-rings were to be installed on the connectors as per a certain kit#. Mine does not have these o-rings so it's either never been done or isn't a model that needs it. Evidently the dealer is to examine the pins and if they're corroded, replace the harness and PCM. I don't know for sure but some of the gold colored pins in the PCM are black......looks like corrosion to me but who know.

The PCM is about the only thing that hasn't been replaced.

Thanks for your idea tho.....if you think of anything else, I'd be interested in hearing.

Rob