I was driving home about a 30 min drive and my GEN light came on, I looked at my volts and it read around 15-16 volts which is more then usual for my truck. My truck never died when the GEN light came on, the light would just come on and turn off after a while. Does it sound like the alternator or something else?

 

Check your alternator and battery connections to make sure they are clean and tight. If they are good, you can disconnect the battery and take the alternator off and take it to an auto parts store to have it checked out.

 

15+ volts is too high and will trigger the light just as too low voltage. Given that the alternator puts out plenty of voltage it's more likely an issue with the voltage regulation circuitry. What year is the truck ?

 

You might want to verify the voltage at the battery with a meter.

 

Bad voltage regulator. Unfortunately, it's part of the PCM.

 

So will I have to replace the whole PCM? And another question what size nut is used for the field terminals on the back of the alternator? 1997 dodge ram 1500 5.9l v8

 

it’s a 97

 

Sounds like you may need another PCM, as the voltage is regulated by the PCM. I believe on a 1997, the PCM is easy to swap and doesn't require a VIN update, unless you possibly have an OEM security system. I've had good luck finding good used PCMs off eBay or car-part.com. You just need to ensure the PCM part number of the replacement PCM matches your original PCMs part number.

 

im gonna get an external voltage regulator so I’m not spending crazy money on a new PCM

 

Understand. There are several videos out there that show how to perform that modification, if desired. Used PCMs aren't terribly expensive either and I've had great luck with them on my truck.