Hey guys, just stumbled onto this site and it looks pretty good. I did some searching but I wanted to see what you guys think. I also posted this on Dodge Talk so I will just be copying and pasting into here. Thanks in advance for all of the help .

 

The truck is a 2004 Ram 1500 with a 4.7l and the 545RFE transmission. It has the NGC computer and has 72k miles on it. Ever since about 60k miles, every now and then the transmission relay would not want to engage. If I cycled the key a few time, it eventually would work. This started out only when it was cold, but then got worse with use.

At about 68-69k we started doing some trouble shooting and trying to figure out why it was doing that. We put a new relay in and wired up some lights from the PCM to the relay and from the relay to the tranny. We also cut open the old relay and the contacts were fried.

At first everything was working fine and then, after a few thousand miles, the relay started not engaging again. First in the winter, when it was cold, then any time. Turning the key off and on a few times would get it to eventually work. The lights indicated we were getting power from the PCM but the relay would not catch. Then, more recently, when I would turn the key on, there would be no power coming from the PCM. Again, cycling the key would get it to come on eventually.

Most recently, I was driving down the highway on a flat road and the transmission would go from OD to 4th and back again and again. It would only do it every now and then. Then one day, going 70 down the highway, the PCM voltage went away and the transmission immediately went into limp mode.

The truck has now been sitting for about a month. I took it to a transmission shop to get them to work on it but after two days they could not find a problem. All wires between the PCM and relay and relay to tranny are good, and the PCM checks out. I did the key dance to find the codes, and the only one was P700, just saying my engine light was on. I then did the hard dump to reset everything and the truck has been running fine now for about 100 miles. This seems to be a problem that develops with use.

So we're pondering getting a used PCM just trying to rule that part out, but thinking there may be a bad ground somewhere? The fluids and filters have not been replaced since I have owned it from ~30kmiles. I was also reading that one feature of the RFE transmissions was the ability to go into limp mode if the computer thinks something may hurt the tranny. I am going to chance the filters and fluids now after learning the importance of it. But could that be causing the PCM to kick the tranny into limp mode? What would be causing the relay to not want to close after some use? This is the second one I'm going to be replacing soon. Could the fuse block be bad?

Another thing I forgot to mention, occasionally very recently, the relay will stick closed with the key off. I can pop the hood and tap on it a few times and it will open up. Does Autozone sell these relays?

 

Some catching up. When I got the truck back from the shop, the engine light was still on. I did the "hard dump" and flashed the codes. I then had a filter change done. The mechanic said the pan looked great and there was nothing on the magnet, he said it looked just like a 70k mile transmission should. I went 300 miles with no problem, and then after the truck sat idling for about an hour, the next time i took off it threw a code.

The codes are:
p0700
p0846
p0871
p0876
p0988

Two different mechanics think a faulty ECM is causing the problem, I seem to want to agree with them. I can get a junkyard ECM for $125 and have it flashed for $100. But I'm not 100% sure it's not the transmission. I don't want to have $300 in ECM and then have to rebuild the tranny and have a spare ECM sitting around. Or, I can take it to a dealer and pay $110/hr to do a transmission diagnostic done on it. I'm not sure what to do.

I don't know if it has anything to do with anything but there is an after market stereo that I installed myself, I know it's right. I also had a remote start installed. A few thousand miles ago, if I were sitting with my foot on the brake with the AC off and either blinker on, the blinker would freak out and stop flashing. The overhead display would also stop. Then, if I tapped the gas or went to high idle from the AC, it would work normally. I had it looked at and they said it was the ignition switch, replaced it and hasn't messed up since. So there is the electrical history if it is any help.

I'm trying to take it to Oklahoma City Sunday so I'm open to some good ideas.

Thanks

 

i would pay the dealer for diagnostic.
they will have to run a special tool on it called the "simulator" where they can manually change gears and control each solenoid. They should be able to figure it out for you fairly easy