Toyota Repair: PO401, intermittent problem, vsv

Question
Hi Ted,

You said previously that the code PO401 on my Rav4 (105,000m) was probably or most likely the egr Modulator or the VSV.  The light has come on and gone off now twice, being on for a day and a half, then 3-4 days.
Which part is or would cause more of an intermittent problem?  I've check the air flow throgh the proper ports on both parts, and a continuity and ground test on the VSV.  All were O. K.

Thank You,

Rick

Answer
The most common failure is the vacuum modulator, remove the plastic top and look for a burned spot on the filter inside, if there is replace it, the problem with the vsv is that they tend to have intermittent problems so we always replace them when the modulator leaks. When checking the modulator make sure no air passes through from the bottom port with the valve removed blow at the bottom port, if air goes through replace it.