P1516 Throttle position not within calibrated range of each other
You have a poor connection when dealing with P1516. Chevy even has a TSB about P1516 caused by a loose wire crimp at the throttle body connector. whcih tends to break about 1/4 from the connector. Another cause can cause by the throttle connection not seating properly or locking properly
Whe dealing with P1516 check the connection from the connection along its harness
This P1516 was set when its locking tab where broken and made poor contact, the fix here was using zip tie to hold it in place.