DTC will set when the following conditions are present:

WARNING: This page is about a different car, the 1997 GMC Savana, 1997 Chevrolet Chevy Van, and 1997 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

Engine is running.
No MAP sensor DTCs are set.
No TP sensor DTCs are set.
No IAC sensor DTCs are set.
MAP is less than 50 kPa.
Change in throttle position is less than 2 percent.
Last throttle position is greater than calculated throttle position based on engine RPM.