Don't know if I have a charging issue or gauge issue.

Once in awhile my volt gauge will go all the way past 18 volts. Sometimes the info center will say battery not charging and the battery light will come on.

If I disconnect both negative battery cables and reconnect it goes back to normal. Sometimes it goes for days without happening other times more often.

New Interstate batteries were put in last year in March.

You could have your alternator checked, not sure if you have to pull it for this or not, but most oriley's advanced autozones will do it for free.

You should get a scanner and check for codes as well.

I would say its just GM's pile o carp gauges, but if the message center is saying it to it may be something else.

matt

I had the alternator in my '11 chevy replaced under warranty for something similar. The charging light would go on and off the volt gauge would read hi sometimes low sometimes and normal sometimes. I drove it for a month like that before I got around to taking it in they replaced it and no more problems but I still have no idea what was wrong with it.

matt

there is a battery module on that truck if memory serves me correct,its a little red box that go's around the positive battery cable and has a plug that go's into it,that could be causing it also,also have the battery tested to make sure you dont have a bad one,a bad battery will cause the altenator to do the same thing its doing.

Thanks Stan.
I was hoping you would see this.
I will get the batteries checked and look at the module. Would the plug just need to be cleaned. I have checked all the cable connections to make sure they are clean.

the module usually will go bad,i can check it here with a tech 2 if the battery's test good.

Thanks.
I will get the batteries checked and let you know.

Stan,
The truck has been running fine until yesterday when the volt gauge acted up again. It did it several times yesterday. I was still able to disconnect the batteries and get it to reset.

This morning I left the job and it did it again. I drove around the corner and the check engine light came on. The truck lost power also. It would idle but the throttle was unresponive. I pulled over and unhooked the batteries and let it reset. The truck ran fine after but the check engine light stayed on. I drove straight to O'Reily auto and had them read the codes. It said the ECM/PCM relay is shorted or faulty.

They said they can't get this part. Is it a dealer item.
I need to get this resolved before it drives me nuts or does some major damage.

Any insight would be appreciated.

Most vehicles have a voltage shut off for the ecm. so if the voltage gets to high the ecm will shut down so it doesnt fry the electrical system. I not sure on the Duramax but most diesels are 16-18 volts depending on the maker, just like 24 volt systems are shut down at 28 volts or over . If you have no way to test the alternator are batterys and the electrical sysytem I would take it to someone who has the correct reader so they can look more into live read out and live data when the problem happens. i have my run ins with those code readers at orielys on big problems like your having and they dont always give the right answer. Like for instance my wifes expedition whould just go into safe mode then turn off. said the maf sensor was bad. I found the throttle boddy was bad and causing the problem.

I would start with checking voltage at batteries with volt meter when it acts up. If voltage is that high, alternator may be bad.