alright i bought a c5 that was wrecked looked over all the wiring everything is great.. car has a ls2 tb on it with the correct harness to go with it, there is a small hole in the throttle body about 3/16 big. i can clear the codes out and it runs good and revs good but if you turn car off and restart it goes back to missing with the reduced engine power and active handling lights on. shows the p1516 code.. tb seems to be working correct just hate to start throwing parts at it that are expensive. have even tried clearing them out twice.. please help if you got anything helpful

 

The code indicates the predicted and actual throttle positions are different. Problem could be with the PCM, TAC or Throttle Body module or the wiring between them. First, disconnect the throttle actuator motor harness connector. Remove the air inlet duct from the throttle body. Inspect the throttle body and the throttle plate for debris, damage, and tampering that could cause the throttle plate to bind. If debris is found, clean the throttle body and repair the source of contamination. If the throttle body and/or throttle plate is damaged, replace the throttle body. Next, slowly open the throttle plate by hand to WOT and return the plate back to the closed position several times. Does the throttle plate move smoothly without binding in both directions? If not replace the throttle body. If the throttle body looks good then check grounds, connector pins for cleanliness/corrosion, pin contact from one side of the connector to the other.

There are some other voltage checks that can be made but probably will not do any good as it sounds like the TB works until the engine is shut off and restarted. That sort of indicates a problem with the mechanical movement of the Throttle Blade.

This code is killing your traction control since the throttle control isn't working properly.
Bill