Conditions For Clearing MIL/DTC

WARNING: This page is about a different car, the 2002 GMC Sierra and 2002 Chevrolet 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.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission-related diagnostic.
A Scan Tool can clear the MIL/DTC.