Conditions For Clearing MIL/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.

The ECM turns OFF the MIL after three consecutive ignition cycles in which the diagnostic test runs and passes.
The ECM cancels the DTC default actions when the fault no longer exists and the DTC passes.
The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
A scan tool can clear the MIL/DTC.