Conditions for Clearing MIL/DTC

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, 2002 Chevrolet RV Cutaway, and 2002 Chevrolet Cutaway. 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.