Conditions For Running DTC

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

DTCs P1282, P1283, P1287, P1288, P1635, or P1639 are not set.
The ignition switch is in the crank or run position.
The ignition voltage is between 7-16 volts.