New to this site Glad I found you .
I have a 02, 3500 with 178000 miles on it. Just recently the volt meter would go from 14 volts to zero volts. Of course the check gage light comes . All the rest of the gages work , turn signals work lights radio etc. all work so I know I have voltage. When you shut the truck off and restart it the volt gage works fine for a time but dies ine about 10 min. or less. Took the truck to a local parts store and tested the batteries and Alt. they said that I needed a new battery and a new Alt. So I replaced them. Didn't fix the problem. I went back and had them recheck the both batteries and the new Alt. they said the battery I had not replaced was now bad and the new Alt was bad I didn't believe them this time . Had the old battery and the old Alt. checked inside the store They were GOOD. Surprise Surprise. I thought the only item left was the gage until my research lead me here and read about the PCM . I have also read that a bad pcm could cause other problems some of which I have. No Cruse being one of them. Other than the PCM are there any other things to check be I go buy one. I/E relays diods ets?
Any help would be great thanks Jeff

 

Check the connection from the gauge cluster to the harness. Lots of times you get a no bus on the odo, but not always.

Corrosion can play funny tricks at connections.

 

Thanks I will check. This morning I noticed the voltage was only about 12 volts so the batteries are running things and it would seem that the Alt. is not charging. I will also have the new Alt checked out again. Thanks

 

The connection at the back of the alternator has about 1mm of extra length, which can cause it to break or short the wires. If your Alternator tests good, check that harness for wear....

 

Thanks
I checked of the wires at the Alt and found them in good condition. What I did find is the voltage is dropping every time I get back in the truck so the Alt is not charging. Also checking the voltage at the Alt I am only getting about 12.5 vdc out of it which is the same output I had on the old Alt which is why I changed it out. Unless I got a bad alt out of the box , which happens a lot ,that puts out the same voltage as the old one then there has to be something keeping the Alt from doing its job. Besides the PCM is there anything else that might cause this type of problem. And thanks for all the help I'm not a great Mech. just ok at best.

 

Guess I would check for codes, it should produce a PCM issue if there is one......

 

Thanks I will check tomorrow

 

Checked. Found no pwr at Alt repaired .Thanks for all the help