Hi everyone,

Received a P0401 trouble code "Insufficient EGR Flow". This is on a 2000 4Runner, 3RZFE engine (2.7, 4cyl).

Went ahead and applied vacuum to the EGR valve, the engine sputtered and stalled, so the EGR valve is working.

Attached a vacuum gauge to Q Port of the Vacuum Modulator, registered 20, so it looks like it's within spec. (Any additional tests I can do to make 100% sure it's NOT the modulator?)

I'm thinking at this point it could be the VSV? Where is this VSV and how can I test it to be sure? Any other suggestions on how to pinpoint the problem? Need to do this so I can pass Virginia emissions.

Thanks everyone!