Interesting ESS issue.

Alright guys I could use some help on this one.


I've been fighting with losing tach signal and thus od and lockup as well as charging for about a year. I've gone through just about every thread I could find on faulty ESS and electrical anomalies. From what I can tell electrical issues are the norm on these trucks.

It was at one point completely intermittent as in once every month or two. I just rebuilt the trans and put the truck back together after sitting for a few months and now after it runs for a few minutes the tach starts bouncing and spiking up.

What I've done:

*replaced ESS/ readjusted several times

*checked / cleaned each pcm connection/ tightened each connection

*ohm tested each leg of the ESS circuit to the PCM .2 ohms each leg

*pulled apart the ENTIRE harness/ no chafing or bare spots to be seen

Here is where it gets interesting; I plug it all back together and now I'm getting 12 volts at the purple and white wire at the ESS!?

Any assistance would be appreciated this issue is really getting the best of my patience. wned:

Have you tried a different PCM?

Not yet. That's my next move at this point. I'm just trying to eliminate any chance of a short being present and toasting another pcm.

Any recommendations on a good pcm rebuilder. The last thing I need is a bum unit out of the box to make me keep searching for an issue that isn't there.

So anyone have a good pcm rebuilder they've used?

The only one I ever tried sent mine back worse than when I pulled it. My 04 just randomly died, when it came back it wouldn't even start. New ecm truck ran fine. I don't recommend "The Car Computer Guys".

96 3500 5x018 7mm dvs 62fmw

To my knowledge there are no "new" pcm's available for the 12v trucks. Even the dealership units are "refurbished" they just cost alot more.

Why am I not surprised. Sorry to hear that, just don't use that place I tried. Like I said after paying them good money the unit they returned to me was worse than when I removed it.

96 3500 5x018 7mm dvs 62fmw

If you can find one you need a powertrain diagnostics procedure manual. It is not the FSM, and it will cost you some $$$ if you do find one. It will have pin outs, troubleshooting, and other valuable information. I've only used mine twice, but the first time I did it payed for itself.