Hey guys, I'm experiencing electrical difficulties. I've been digging through my Chrysler Full Service Manual and searching the posts on here and I think I have it narrowed down to the PCM as the cause but I don't know if the PCM itself is bad. Here's alist of the symptoms:

No "Wait To Start" light
Alternator is not charging
No dash guages period (not just tach and speedometer. NONE!)
Odometer shows the mileage but does not move when driven and flashes
No overdrive
No TCC lock-up
Starts out in 2nd gear

It started all these symptoms at once. I have already checked the Crankshaft Position Sensor and it appears to be good. The truck I'm working on is in my sig. and I put a computer out of a 1998 5-speed truck in there and nothing changed. I know the 5-speed PCM will not work my truck's tranny solenoids, but according to my Chrysler Service Manual all the other pins should be the same (i.e., it should work the dash guages, grid heaters, etc.) Does anybody out there know where the PCM grounds to the frame? According the to FSM pins # 31 & 32 in the C1 plug are grounds but it doesn't show where they actually ground to the frame. Thanks!

 

to test the ur theory why not run another ground from ur pcm ground wires directly to the battery. that wud give u a leg up on whether or not u really need to find those grounds

 

I assume the manual tranny PCM you swapped in came from a donor truck that was working fine.
Before you condemn your PCM as bad try using it it in the donor truck.
It could be not all functions will work correctly but most should if your PCM is good.

 

OK, I found the problem. It was the Crank sensor. Evidently, it had an internal short and was causing the PCM to go into protect mode. As a result, anything controlled by the computer was dead.

 

you gotta love electrical problems. i had the same sorta nightmare with a 03 ford sic.0

 

Yeah, I was absolutely about to pull my hair out. But, I finally figured it out. I HATE ELECTRONIC PROBLEMS!

 

I’ve read a lot about the no tach, no charging problem on my 1995 Dodge Cummins, but haven’t seen my exact problem.

I turn the key on and I don’t get the “wait to start”, “trans temp”, “water in fuel” lights for at least a minute and considerably longer if it is colder outside. So far, it has always eventually come on and then the tach and alternator work.

Sometimes I have driven the truck miles before these lights came on. Once it is taching and charging, it stays working until I shut it down.

Another strange thing is that when the lights start to come on, they start dim, flicker on and off as they get brighter and I can hear the fuel pump relay chattering away in unison with the lights flickering. After sitting over night, the flickering takes longer to start and can last for 30 seconds before the lights go soild and then off.

I’ve read that ESS effects charging and tach, but would it make the lights circuit do what it is doing. I’ve unplugged the ESS, go to start the truck, the lights do the flickering thing, but the tach and alt don’t work once engine is running (as expected). I plugged ESS back in and after flickering, it charges and tach works. (leading me to believe the ESS is good) What could cause the delay and flickering?

And just recently, the truck takes longer to go into overdrive and the cruise control shuts off after hitting a bump. Any thoughts or ideas? I’m leaning towards ECM (pcm), but many of you say they are pretty sturdy.

I would be willing to call you on the phone if you think you can help.

 

Golf have you tried another ess? also maybe try unplugging other sensors one at a time to see if there is any difference. also maybe see if you can pick up a pcm from a wrecking yard for cheap. have you gone over all of ur grounds?

 

CJ, I ordered the Dodge Service Repair Manual and will start checking out the wiring, grounds and sensors when it arrives. I am reluctant to start replacing parts (ess, pcm) without a little more research. Thank you for the ideas. I am guessing the pcm would have to be programmed for my truck, correct?

 

Just for grins, have you removed the 3 PCM plugs, checked for corrosion/etc and reseated them?

Perhaps it takes them warming up to establish good contact?

Can't hurt anything.......

 

'95 only has one PCM plug, and it's really cheap.
The female connectors tend to enlarge or break so they don't make good contact.
Seems like the connector was designed to only be plugged in once.
They really get messed up if a person pushes meter probes into the females.
What I've had to do is check the females one at a time and use a needle to close enlarged contacts smaller. Made three supposedly bad PCMs work perfect again with this time consuming method.

 

Good to know Bill....... Wonder if then 96 is when they went to 3 connectors?

 

Thank you for all the ideas. Still waiting for the manual to arrive and haven't had much time to troubleshoot.
I disconnected some of the sensors and checked for 5vdc coming from the pcm and it wasn't an immediate 5 vdc (it gradually went to 5vdc as the wait to start light flickered and got brighter) Takes longer if it is colder outside.
Also hooked the meter to the chattering fuel pump relay coil (across 85 and 86) and the voltage gradually went to 12vdc. Once it gets 12vdc, the chattering stops, and the WTS light goes steady and bright.
I plan on verifying good ground and power connections to the pcm and will heed the advice about pcm plug connections. Then I will start checking outputs from the pcm. I will post my findings.

 

The factory service manual doesn't really get into the electronic control system.
For that you need the manual below. Unfortunately it's out of print, was only $10 fifteen years ago.
See them on ebay quite often for around $20.

 

I purchased and am currently waiting for a Powertrain Diagnostic Manual (PDM) from eBay. Been checking grounds and power to the PCM and all seems ok. I also ordered an ESS.

The ESS connector is C178 and has 3 pins. Looking at the plug holding the wires in your hand, the top pin (#1) is 8vdc supply, the lower left pin (#3) is the ESS signal (I am getting 5vdc there at all times, hope this is right?) and the lower right pin (#2) is the sensor ground.

I do not have access to another PCM to try swapping it out. My truck is the one in my signature, does anyone have a working PCM for it if I end up going that way?

Thank you