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PO401 low flow

(1997 Toyota RAV4)
in Bath, NY on August 17, 2011
replaced VSV & modulator. With EGR tube off and vacuum pump attached modulator port Q,with ing. on no reading. Sometimes I have vac. at Q when ing. is off,wnen turned on I loose Vac. I think maybe i have a prob. with the connection at the VSV. What should the voltage at the VSV connection? codes (2) both po401

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Popular Answer
on August 18, 2011
I would go to this link and follow this article. I wrote this as I do Emissions Diagnosis and Repair at a Gold Shield Station in Calif. A P0401 is somewhat common on Toyota and they can be stubborn to resolve. The passages have to be 'perfecto' clean and I have seen a few of the vacuum solenoids fail on an intermittent basis. It is common for the transducer to become weak as well.

http://repairpal.com/OBD-II-Code-P0401-Toyota
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