P1516 ghost problem

I have been looking at a 2003 cadillac ext with a 6.0 for a friend. they say when you let the truck idle for 20 minutes in the morning it will start to lope and miss. it then displays reduced engine power and wont hardly move. the throttle body was replaced with a new gm part 6 months ago and has been fine until now. the throttle body pigtail and tac module have been replaced with known good parts. the battery is also new. it still acts up for them but i have never seen it myself after several hours of running. i unplugged the tac module and used a power probe 3 to check the ground and it trips the breaker so it must be ok. i cant get my hands behind the head to get the grounds loose to inspect them but everything seems tight. i have wiggled the wiring while watching the scanner and there are no spikes or dropouts.i hook up a snapon modis and watch the throttle data and everything looks fine except maybe once every 30 minutes the app and tps voltage drops to 0 volts for a millisecond then its back to normal. it does not set a code or act up when this happens. occasionally the scanner will lose communication as well. anyone had a similar problem? thanks in advance

im having the same problem!! have you figured it out yet?

I had the same problem a few years ago. I spliced into the ground for the tac module a couple inches away from the plug and ran an extra ground to clean sheet metal close to the module. Problem solved after doing this.

I had the same problem a few years ago. I spliced into the ground for the tac module a couple inches away from the plug and ran an extra ground to clean sheet metal close to the module. Problem solved after doing this.



Thank you. I will try it out and let you know.