2WD (4A-GE)

Tee a vacuum gauge into vacuum line between the vacuum switching valve and the Toyota Variable Induction System (T-VIS) diaphragm. Connect tachometer to engine. See ADJUSTMENTS article for correct tachometer attachment.
Start engine and warm to normal operating temperature. Vacuum gauge should show high vacuum at idle (internal throttle valve closed).
Increase engine speed to above 5000 RPM. Vacuum gauge should indicate zero. If not, test vacuum switching valve and use hand held vacuum pump to test if T-VIS diaphragm holds vacuum.

Fig 1: Testing Variable Induction System
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
To test vacuum switching valve, remove valve from vehicle.
NOTE: Testing for T-VIS vacuum switching valve is not available for Corolla
Ensure there is no continuity between wiring terminals and body of valve. To check air flow through valve, see Fig 1.