I have a 2000 Chevy 2500 with 6.0 eng with Service Eng Soon light on. Tryed 3 different Readers, 2 Actron, 1 Snap On model and neither will power up to read fault code. Instructions on Actron reader says you have to have 8-16 volts on #4 Grd and #16 Pos to power up unit. I have no voltage there. Any help on where next to look. Thanks in advance on any help!

You should have a cigarette lighter adapter for the DC power input. And if it's a good unit it should have battery back up fail safe.

I strongly suggest obtaining an accurate wiring diagram and locating the problem. It is likely that the lost voltage and the SES light are related. Check the obvious before jumping to conclusions. It is always best to fix the obvious before proceeding. Ray

Thanks to both of you. I will try to find a wiring diagram to find out why I have no voltage at the socket. As for the DC voltage for the scanners I tried, I don't think there are any other power source other than from the one provided by the socket, according to what I read. Other than the SES light, truck is running fine, but what about at inspection time? Got to get her fixed. If anyone else can shed some light, please do so.

check all the fuses.

more specifically check the cigarette lighter fuel under the hood at the power distribution box

The cigar fuse was blown. Changed it and now good to go. SES light also went out on it's own. Thanks to all your help!