Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The PCM turns OFF the MIL during the third consecutive trip, in which the diagnostic test runs and passes.
A scan tool can clear the MIL/DTC.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission-related diagnostic.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.