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 speed is less than 4000 RPM.
MAF sensor is at least 5 gm/s.
Crank sensor duty cycle is greater than 50 percent (or the ratio high ref/low ref is greater than 5.66).