DTC will set when the following conditions are present:

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1997 GMC Savana Special, 1997 GMC Savana Camper Special, 1997 GMC Savana, 1997 Chevrolet RV Cutaway, and 1997 Chevrolet Cutaway. 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.