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.

System voltage is greater than 9 volts but less than 17 volts.
MAF is less than 27 gm/s.
Engine run time is greater than 2 seconds.
Engine coolant temperature is less than 90°F (32°C).
Intake air temperature is less than 90°F (32°C).
Difference between engine coolant temperature and intake air temperature is less than 41°F (5°C).
Difference between engine coolant temperature and intake air temperature is less than 47°F (8°C).
Elapsed time to obtain .3-.6 volt is greater than calculated value.