Conditions For Clearing MIL/DTC

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The PCM turns OFF the MIL after 3 consecutive ignition cycles in which the diagnostic test runs and passes.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A Scan Tool can clear the MIL/DTC.