Pickup & 4RUNNER

Warm engine to normal operating temperature. Increase and maintain engine speed at 2000 RPM. Unplug connectors at Electronic Air Control Valve (EACV) and at Electronic Bleed Control Valve (EBCV) and wait a few seconds. See Fig 2.
Reconnect EBCV connector and ensure engine speed drops about 300 RPM. Disconnect and plug vacuum hose from vacuum switch. Ensure engine speed returns to 2000 RPM after a few seconds. Reconnect vacuum hose and connectors. If no problem is found, system is okay.

Fig 1: Fuel Feedback Control System Testing (Corolla, Tercel Sedan & Wagon)

Fig 2: Fuel Feedback Control System Testing (Pickup & 4Runner)