Description of 2 Trip Detection Logic
Diagnostic codes 21, 25, 26, 27 and 71 use "2 trip detection logic". With this logic, when a malfunction is first detected, the malfunction is temporarily stored in the ECU memory. If the same code is detected again during the second drive test, this second detection causes the "CHECK ENGINE" warning light to light up.
The 2 trip repeats the same mode the 2nd time. (However, the ignition switch must be turned OFF between the 1st and 2nd time.