Vacuum Modulator Valve
Vacuum modulator valve (VMV) helps regulate EGR valve opening. The VMV allows increase in vacuum to EGR valve as throttle closes. To test VMV, connect vacuum gauge to port 2. With engine idling, vacuum reading should be about 14 in. Hg. Connect vacuum gauge to port 1. Vacuum reading should drop to about 13 in. Hg. See Fig 1.