DTC will set when the following conditions are present:

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1997 GMC Yukon, 1997 GMC Suburban, 1997 GMC Pickup, 1997 GMC Cab & Chassis, and 1997 Chevrolet Tahoe. 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 60 kPa.
Change in throttle position is less than 2 percent.
Last throttle position is greater than calculated throttle position based on engine RPM.