Test Conditions:

Codes EO21, EO22 and EO24 are not set. Vehicle in coast down condition. Throttle switch open, brakes applied, throttle angle is 16.5 degrees or less and RPM is greater than desired.

Under these conditions, the PCM commands the ISC to retract and extend and monitors the TPS a corresponding decrease and increase in throttle position.

If PCM detects a decrease and increase in throttle position twice in succession, then the code will set and SERVICE ENGINE SOON light will turn on.