I have a 2002 Dodge Dakota SXT, it's in the shop right now, they have a guy out driving it trying to reproduce the problem, which is:

You're driving along for several hours, everything is fine, then the battery indicator gauge starts going down, slowly at first, then drops all the way to zero. Check Gauges light comes on. Truck running fine. IF you keep going for another 30 minutes, maybe an hour or so, then the computer will start shutting electrical subsystems off until eventually it will shut the whole vehicle down.
The first time it did this, I had it towed to the Dodge Dealer. Next day, they called and said nothing is wrong, battery and alternator good. The battery terminals just needed tightening, perhaps, and thats all they did.
I picked it up from them, drove it to work (4 miles) and back for several weeks no issues.

Then, went on a road trip, drove it a couple hours down a US highway, started acting same way, but we stopped for a while, I checked wires, grounds, etc. Couldn't see anything obvious. Started back up no issues rest of day.

Back and forth to work for several weeks, no problem. Left on LONG road trip from Oregon to Arizona. Started out at 9am, few short rest stops, then at 4pm started doing the crap again. Stopped at hotel.
Next morning, seemed fine again, 50 miles down road, same stuff starts happening again. Took it to shop where it is now. I was able to show them the low voltage on the gauge, but since they didn'[t start working on it for a couple days, it seems ok to them, so they have someone out driving it to get it good and warmed up, so hopefully they can reproduce it.
Another data point is that when it is in this failure mode, if you stop and shut the engine off, then you turn the key back on, it will show about 6 volts, then about 2 minutes after you get going down the road it will go back to zero and check gauges light will come on again. It will do this repeatedly until you shut it off for a good long while, like overnight. Could it be the PCM has a heat problem? Has anyone seen anything like this?

 

Welcome to the forum.

Did you have any codes? You don't need a scanner on a Dakota. With the key OFF, turn it to RUN (don't start the truck) then back to OFF, then to RUN, back to OFF, and then LEAVE IT in RUN. Codes will display in the odometer. P DONE will display when finished.

It does sound like a PCM issue. Obviously you've never had 0 volts and very likely not 6 either. The gauges are ALL computer driven from the PCM - it really isn't the typical voltmeter. It would help if you could get some real readings, using a multimeter, when this was happening.

If you need a new PCM be sure to look online for a reman'd PCM. You just provide them some information and they'll program it for your specific truck. The dealer is $$$.

 

I tried to get codes, assuming I did the sequence correctly, there were no codes.

Right now, I am in AZ and the truck is back in Chico, California at "Dr of Motors". That's near where it started acting up. They seemed to have a pretty good reputation from several online review sites, so I had to make a decision as I did not want to get out in the middle of the desert between Bakersfield and Phoenix, and break down, it still being summer and all : ) Would be a huge tow bill!

So I left it with them and took a rental car the rest of the way to Phoenix. They just started looking at it today, and of course, it's acting normally. They said they have someone out driving it to get it good and hot and hopefully it will start acting up. If they can't reproduce it before too long, I am thinking of taking a risk, and just have them replace the PCM, and hope for the best
As it is, I will need to fly to Sacramento, drive a rental to Chico, pick up the truck, and try to drive it to Phoenix (850 miles).
I really like this truck, she's 12 years old, 197,000 miles, and been a sweet one for me over the years. Brakes, Clutch, and Rear Differential is only major stuff I've ever had to have done on it.

 

I'm no expert on auto electrical or possible PCM/computer stuff but you may have a bad battery like a cracked cell inside how it works is at most battery temps it works fine but as it heats up the cracked cell opens up and causes problems. This also can explain why its so hard for a shop to find the problem as the battery needs to get hot/warm before anything happens.


I had a friends car that had the same weird no one could figure out the problem till my Dad figured it out like he had seen it many times in his auto working days.

 

This may help explain things more


http://batteryuniversity.com/learn/a...internal_short

 

+1 on bad cell in the battery. Bad cells are a big problem here in the Florida heat, probably about the same or worse out West. It may be best to start with the most simple and least expensive solutions first. Try a new battery and see what happens from there. Then if the problem persists it could be the voltage regulator, if so you will need a new or rebuilt PCM because the regulator is an internal part of the PCM. When the truck has the problem check the battery and alternator output with a voltmeter like Dan suggested, your actual voltage info may help identify the problem.

Jimmy

 

I tried a new battery the first time it happened. It would be a coincidence if 2 batteries in a row did the same thing.

 

Don't rule it out, believe it or not my father had the alternator on his RAV4 replaced 3 times. 2 replacements were bad.

 

Yea unfortunately I've seen all too many NEW things that were bad over the years the worst was a new rad that had half the core was plugged up car over heated almost as fast as it got to stat temp and blew the rad cap off with a loud pop.

I don't know why but anything related to an auto has more of such bad crap

But two batteries maybe not almost every Dakota PCM dies on you one time its not when it will happen because it will happen guaranteed.

 

Is there any way it could be the alternator?