PCM wiring harness problem

[Jdonoghue]

I've got a bad connection somewhere in the wiring harness that goes to the PCM. Normally, when I turn the key on, the 'water in fuel' and 'wait to start' lights come on for a coulpe of seconds. They don't anymore (or I hear this 'buzzing' and the 'wait to start' light flickers). Also, when this happens, the alternator won't charge the battery.
If I grab the wiring harness and move it around, then try again, everything works for a while (it stops charging somewhere down the road, though. )
I've checked/cleaned the ground connection to the body (the one near the battery), it has a good connection.
Are there any other grounds I could check? I can't see any. There isn't any visible damage to any of the other wires or connections. Is there something common in this area that I can check? It's been doing this for a few days, I hope I don't fry something by driving it.

 

[1stgen4evr]

fry something

Only thing you will fry is your brain and wallet trying to make the PCM work. You may indeed have a connection that is bad or you may have a bad PCM. Chances are you will never know. I spent a ton of money on a 93 trying to make the PCM do its job and finally parked the truck. Intermittent OD, faulty alternator, eratic AC, misc lights, you name it. The Piece o Crap Mother is the problem. Bought a 89 and plan to refit the electrical to the earlier setup. If you remove the connection from the pcm and look at the hookup, you will see a design that might work for a cheap radio but not too good for a truck.



The PCM and the lack of a real four door truck is the only reason Dodge has not taken the light truck market.



Good luck whatever you do.



1stgen4evr

James

 

[DCTECH]

THE PROBLEM IS INSIDE THE PCM CIRCUIT BOARD IS LOOSE OR BROKEN. REPLACE PCM AND WILL BE OK. i HAVE REPLACED SEVERAL OF THESE WITH THIS PROBLEM.

 

[Jdonoghue]

Originally posted by DCTECH
THE PROBLEM IS INSIDE THE PCM CIRCUIT BOARD IS LOOSE OR BROKEN. REPLACE PCM AND WILL BE OK. i HAVE REPLACED SEVERAL OF THESE WITH THIS PROBLEM.

Circuit board, eh? Good thing I spent several years doing circuit board work... time to dig out the 'ol soldering iron!

 

[Jdonoghue]

Ugh

The PCM is potted (non-repairable). So I put it back in. I'll see what happens tomorrow morning (the problem seems to occur most often in the morning).

Due to the potted nature of the PCM, I'm inclined to think there is a bad connection somewhere else.

 

[dpuckett]

You can rewire the alternator/ volt regulator and bypass the PCM if you can live with the check engine light always on; or do like I did and pull the bulb. Wish I had made a diagram of the 93 I had that done to... . Funny thing is, the 93 had a reman PCM that wasnt a year old yet. Not sure about the rest of it. ANd people wonder why I put up with my old jalopy?



Daniel

 

[Jdonoghue]

We'll see what happens over the next few days... I went to start the truck this morning, no 'water in fuel' or 'wait to start', and no charge. Spent a while checking everything again - no good. Then I got the idea of checking the fuse block. After I found it, noticed that the 'guages' fuse was not right - a 2 amp fuse wrapped with gum wrapper (foil) I removed the 'fuse' and went looking for a new one. Had none. So I stole the fuse for the radio. It worked! WTF does the guages fuse have to do with the PCM? And why did my guages still work while this was going on?
Anyway, it worked fine the whole time this morning, I noticed that the volts guage reads a little higher than it did before the whole fuse incident. Now I just have to get some fuses so I can listen to the radio again.

 

[Scot]

Originally posted by Jdonoghue

a 2 amp fuse wrapped with gum wrapper (foil) I removed the 'fuse' and went looking for a new one.

Could be worse. I bought a truck and the PO had substituted a 1/4" rod for a fuse.