DTC will test when the following conditions are present:

WARNING: This page is about a different car, the 1997 GMC Pickup and 1997 Chevrolet Pickup. However, it is still accessible from the selected car via links, so may be relevant.

No TP sensor DTCs are set.
No ECT sensor DTCs are set.
Engine coolant temperature is greater than 162°F (72°C).
Intake air temperature is greater than -13°F (-25°C).
BARO is greater than 70 kPa (less than 10,300 ft.).
VSS is less than 2 MPH.
No VSS DTCs are set.
No MAP sensor DTCs are set.
System voltage is greater than 10 volts but less than 18 volts.
Engine run time is greater than 30 seconds.
Throttle position is less than one percent.
All conditions are met for greater than 3 seconds.