98 12 valve not charging
 

I think I have a pcm issue. 98 12 valve manual swapped transmission. I’ve got a few issues my main issue is my alternator isn’t charging. Most of my gauges went out. There is power to my cluster no speed, tack, fuel. Lights light up including my gas light on all time and tank is full. With the key in the on position I have .5 volts to the crank positioning sensor. I would think that should mean the pcm isn’t sending the proper volts to the crank position sensor.
does anyone have some more ideas I can troubleshoot? Voltages to check on pins at my pcm possibly?
thank you for any help I appreciate it

I like to start with the mess of grounds under the drivers side battery. They tend to get corroded due to location.

After preaching so many years, both here and elsewhere, of the importance of grounds, I got caught in my own trap last week...One of my foglights quit working, and since I bought the cheapest incandescent ones on Amazon I figured I needed to replace the sealed unit...I ordered new ones, and after arrival I started taking the old one off when I noticed the ground wire seemed stiff and swollen...Turns out there was a rub through in the insulation where moisture entered and corroded the copper wire inside, breaking the circuit...I had power to the foglight, so after soldering and sealing in a new wire, I have foglights again...

Now I have a new pair of 18 watt LED foglights that I'll have to find a home for...I violated my own #1 rule, "Test, don't guess" and paid the price...:confused:...Ben

It's possible you have a short somewhere that is pulling down voltage to multiple components - the variety and location of symptoms makes that look somewhat unlikely, but engineers may handle power/ground distribution in ways that seems strange to us. Do you have a factory service manual or other access to wiring diagrams? (Check your private messages) Look for power and ground supplies that are common to your symptom areas.

When you turn the key to the run position (not start), do the Wait To Start, Water In Fuel, Gen lights briefly flash on, then off? Those, and any other indicator lights controlled by the PCM, give something of an indicator if the PCM is alive or dead. If you don't get that bulb-check/self-test, then the PCM may be dead or at least not getting power/ground. You said you have power to the cluster - how about ground, and what about power/ground to the PCM?

Thank you for the replies. The gauge lights all light up briefly with key turned to on position. But they do exactly the same if I have the pcm completely isolated. Out of the three harnesses that plug into the pcm does anyone by chance know what pins should have power and if it’s the full 12 volts they should have?

Maybe complete coincidence but all of these issues started with my fuel shut off solenoid going out and leaving me stranded on the side of the free way. I zip tied it in the up position and tada my truck ran again we were off to the races. From the time it died when that solenoid went out my trip meter, mileage, all gauges other than some lights in cluster, alternator not charging, all started.

Dumb question, but did you check all the fuses? I've seen in other threads that fuse 9 feeds more than it's name indicates, and some of the recipients might explain your problems if not getting power - though I don't know if the same applies to a '98 12-valve since Dodge did some things differently for that partial year before the 24-valves came in. Did you download the FSM from the link I PMed you?

Do a Google search for "1996 dodge 2500 cummins fuse 9" or "dodge 2500 cummins fuse 9" (add 1998 into the search if you wish)
Here's one interesting result... (note that it mentioned PCM feed...)

I know I checked fuses originally I will re check. Thank you.
and yes I’ve been reading the manual trying to also diagnose my issue thank you for that. Very helpful.

Fuses are all good. I did an external voltage regulator today and now I have my alternator at least charging again. Still no working gauges tho. I’m guessing my pcm is shot.

I triple checked my fuses actually with a test light today. The fuse panel in the cab fuse 6 is illum has no power. The fuse is good but that one fuse gets no power. How is that possible isn’t the fuse bar a bus bar on the hot side?

Wire it separately unless you want to start looking for the broken circuit...I know what my choice would be...:banghead...Ben

My truck is charging at 16.7 volts now doesn’t that seem very high?

Damaged contacts on the fuse holder?

If it is continually charging at 16.7v, I think that is too high. My Modis scan tool has a test where you can control alternator field and watch the voltage respond - I recall that either the test notes or the FSM say not to let it stay at 16+ volts for very long. Does the external regulator have any adjustment?

No adjustment on it. I took it back today and tried another one same outcome if you give it throttle goes clear up to 17 volts. Alternator is new I replaced it thinking it was my original issue. I grounded the regulator with an extra ground. The lead going to the alternator from the vr is 5.9 volts. I’m at a loss here.

So I wired a relay in in front of the voltage regulator and it got my charging down to 14-14.5 volts. Then I ran to town now we are back to not charging again. I got something funky going on. My fuel shut off solenoid didn’t want to work after I shut the truck off I just worked it by had a couple times then it fired. And now I’m back to truck not charging.

Did the FSS fail to lift this last time, or fail to hold? It is a new FSS? And what happened with the previous FSS? Since it left you on the roadside, I suspect the hold side quit, but best to confirm. If the FSS stays on in "pull" or "lift", I've head of that causing problems - usually with the starter, though.

I'm not familiar with the wiring for an external voltage regulator, but I wonder if you have an intermittent break under the insulation somewhere in your wiring - or in the alternator. As a start, try doing a voltage-drop test on the +-to-+ battery cable, combined with a wiggle test, right after starting the truck. Look for excessive voltage drop or changes as you wiggle the cable along it's length. If nothing there, look at the wiring to the external regulator. If nothing there, suspect the alternator (even though it's "new"). Alternators have been known to short internally - check for a warm area on the alternator after everything should have cooled down to ambient air temperature. Can anyone else think of any areas to check?

Did you replace the alternator before starting the thread or during the thread?