Condition No. 1:

WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 1998 GMC Savana Special, 1998 GMC Savana Camper Special, 1998 GMC Savana, 1998 Chevrolet RV Cutaway, and 1998 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

This condition detects an illegal switch combination.

System voltage is 10-17 volts
Engine is running at more than 475 RPM for more than one minute.
VCM detects an illegal TFP state.
All conditions are met for 7 seconds.