Just bought a 99 2500

Hi Folks,
I just bought a 99 GMC Sierra 2500. 6.0 4x4. The volt meter is reading about 9 volts and the battery icon is showing in the message center. I am thinking alternator, or bad connection at the battery. Anyone have any input? Also have an 02 Silverado 1500. My check engine light is on. Any suggestions other than taking it to a dealer?
Thanks, Tim

for the 99 check all terminals for the battery. Including the little red case right next to the altinator. Tighten all the bolts down then when you jump into the truck idle it for a few seconds if no change then rev the engine a couple times and see if it changes then if still no drastic change when you gas it then check to see if either the batt is dead by replacing it if the new batt sits down at 9volts then its the alti. As for the 02, are you noticing any sputters, hard driving, involintary throttle response, if none of these check to make sure 1. your o2 sensors are properly secure and are not dead. 2. The your MASS AIR FLOW SENSOR is not descreened or corroted. Another thing to check for is build up of carbon and other gunk in the intake tube or TB. Note if you see gunk do not use sprays of any kind to clean this you want to clean it the best you can without the sprays use a towel and some good elbow greese to get it off!!!!! Hope that helps

Thanks for the tips, I will give it a try.
Thanks, Tim

No problem let me know if i can help anymore!

Take your 02 to someone that has an OBDII scanner. A lot of parts stores will let you borrow one in their parking lot in hopes of selling you something. It will give you a code that you look up in the scanner's manual and it will tell you what is causing the engine light to come on. For the '99 I would bet on the alt if the terminals are tight. If the alt was putting out the correct voltage the light wouldn't be on.
Sonny01

I agree with 01Blackerado, but don't go throwing parts at this. That is like finding a needle in a hay stack... OBDII is great, use it. It will point you almost directly at the problem. Autozone will scan for free, but they only get the generic P#### codes. They will not get you a true scan, they can only read the codes. And even then they cant get your tranny codes and ABS. I would take it to a mechanic and tell him that you only want the computer scanned and that you want to know what the SES light is on for. There is a mechanic here in town (Bicknell, IN) that will scan the codes with his Snap-on Scanner (not a code reader like Autozone) for $10. I know that is really cheap, the next place higher charges 45 for it, so you are going to have to look around for a cheap place.

For the 99, defiantley check the alt terminals, and the bat terminals. The alt terminals can corrode just like a battery's from a bad connection.