Two-Trip Detection Logic

WARNING: This page is about a different car, the 2003 Toyota Camry Solara. However, it is still accessible from the selected car via links, so may be relevant.

The diagnosis system operates in the normal mode during normal vehicle use. It also has a check mode for technicians to simulate malfunction symptoms and trouble shoot. Most DTCs use 2 trip detection logic (when a malfunction is first detected, the malfunction is temporarily stored in the ECM memory, 1st trip) to prevent erroneous detection and ensure a thorough malfunction detection. By switching the ECM to the check mode when trouble shooting, a technician can cause the MIL to light up for a malfunction that is only detected once or momentarily (hand-held tester only). See NORMAL MODE CODE RETRIEVAL under RETRIEVING DIAGNOSTIC TROUBLE CODES.

If the same malfunction is detected again during the second drive test, this second detection causes the MIL to light up (2nd trip), however the ignition switch must be turned OFF between the 1st trip and 2nd trip.