Relationship Between MIL, DTC and Detectable Items

WARNING: This page is about a different car, the 2004 Ford Pickup Heritage. However, it is still accessible from the selected car via links, so may be relevant.

When a fault is detected for the first time the DTC is stored in the AFCM memory.
When the same fault is detected in two consecutive trips or if the fault is emission related, the PCM will illuminate the MIL.
The PCM will cease MIL illumination if the fault condition no longer exists or when the vehicle is driven two times with no fault detected. The PCM will also cease MIL illumination if the vehicle auto-switches to gasoline. The drive cycle is counted only when the recorded driving pattern is met. If another fault occurs while counting, the counter will reset.
The DTC can be displayed until the vehicle is driven 40 times.