I have a 2002 Dodge Ram 1500 with an electrical issue affecting the transmission. It's long winded, I am sorry, just wanted all the facts out there. When you start the truck the PRND12 is lit up but there is no box around the P. You can shift into any gear without touching the brake pedal and satill no box around any gear. In order to drive the truck you have to drop it down into 1st or 2nd, then shift it to D once you get going. The electrical side of the trans does not shift so you only get what I believe is 2nd and 4th gear per the manual I looked at. No codes what so ever when you hook in an OBD2 tester. I bought the truck well used, 198K miles, and the first thing that happened was the shifter got stuck in 1st gear, which I broke the cable trying to get it out. I replaced the cable and went on about my business. The issues kept coming and the previous owner had told me he replaced the solenoid pack with a new one because it would stutter and die in idle. He said it fixed the problem for a long time, but when I got it it started again. Somewhere in there is when the PRND12 started doing it's thing. I replaced the solenoid valve pack (white plug option), TRS plate (supposedly because of switching to white plug), and valve body all in one shot, as well as the other 3 external transmission sensors. Problem was still there. I tossed in a new Transmission control module, no change. I properly rigged the shift cable per the manual, once I downloaded it, and the PRND12 cam back and all was well. Drove it a few times and no PRND12 again. I think the cable rig was coincidence because I went back to it and moved it all over with no change. I am a decent wrench, but this one has me absolutely stumped and ready to throw in the towel. I called a few transmission shops and they do not want to even look at it. I do not want to end up at a dealership!

 

Where does the prndl get its clue from? Is it a sensor on the trans, or elsewhere?

 

That's what I am not 100% sure about. I assumed it was through the solenoid pack via the TCM that's why I replaced both. I am stuck?

 

Do you have the service manual for your truck? If so, find the wiring diagram, and see where it gets its clue from. I suspect, that since the cluster doesn't know what gear you are in, the PCM may not either, hence, it doesn't know what to do, so, it defaults to 'not do anything'. On the older trucks, it was just a switch down on the trans, by the linkage. I really don't know how it is supposed to work on the newer ones....

 

So the transmission range sensor, which is on the valve body sends the info to the TCM, and the TCM sends it to the instrument cluster to display PRND12. When you slide the gear shift down into whichever gear, it slides that TRS plate and the solenoid pack has pickups that read the gear you are in. All of that is brand new, that's the rub. I guess I will have to try and ring it all out again.

 

Check the wiring.

 

I have already done that and have been unable to find an issue. I think it has something to do with the contacts between the TRS plate and the TRS itself. I was hoping someone on this forum had heard of this issue or has seen any other Ram with these symptoms.

 

Apparently, there is another active thread about 2008 truck with pretty much the same issue.