Two-Trip Detection Logic
WARNING: This page is about a different car, the 2002 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.
Two-trip detection logic is used to prevent erroneous malfunction detection. 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 that a 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 2-Trip Detection Logic and only applies to specified DTCs.
NOTE:
When road testing vehicle in CHECK mode (Lexus scan tool only), Two Trip Detection Logic will be disabled, and MIL will illuminate first time a malfunction is detected.