Two-Trip Detection Logic
When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate. The second time malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as the 2-Trip Detection Logic and only applies to specific DTCs.
NOTE:
When road testing vehicle in CHECK mode (Toyota scan tool only), the Two Trip Detection Logic will not function. Also, MIL will illuminate first time a malfunction is detected.