Trying to fix P0401 DTC

[PatrickGSR94]

Our 96 7A-FE Corolla has been throwing a P0401 trouble code for a couple of months now. With some searching I found this post on the net:

http://www.corolland.com/forums/inde...ost__p__132780

Says that the EGR modulator should hold vacuum applied to the bottom port.

First I blew air through port Q, and it came out port R. Then I covered R and P and blew air, and the air came out around the filter.

Next I applied vacuum to the bottom port. Now at first it seemed to hold vacuum. Then I blew air through Q while holding vacuum on the bottom port, and then suddenly the vacuum would no longer hold.

So now I cannot get vacuum to hold on the bottom port. I guess I blew through the diaphragm. If I replace the modulator, I don't know if that would fix my P0401 code, or if this is now going to introduce any additional codes or not.

I have also read that the EGR vacuum switching valve is a common culprit for the P0401 code, but I can't seem to find one new. I can only find used ones on eBay and such, and there's no guarantee that those will work.

I also recently saw this post: Here we go again, with more problems... I do plan on removing the upper half of the intake manifold and cleaning it all out, whenever I can get around to it and purchase new manifold and throttle body gaskets. I'm sure there's plenty of gunk in there with 220K miles on the engine.

Any other suggestions?

[PatrickGSR94]

Anyone have any suggestions?

[itreflop117]

Originally Posted by PatrickGSR94

Anyone have any suggestions?

yea, i was the one who posted that thread. but what i found out was, that you should clean the EGR valve. I tried it and it made it turn off for awhile... and then after that it came back on. Then I noticed the EGR modulator (spaceship looking thing with PQR) didn't have a cap on it... since it's a vacuum and doesn't have a cap... there's no vacuum lol if you get what i mean. As stupid as this sounds make sure it has a cap on it. because mine didn't. I got a used one off of ebay with a cap. and now it works perfetly fine good luck man! =D

[PatrickGSR94]

Yeah mine has the cap, and the little filter inside of it. But the bottom port no longer holds a vacuum when I stick it on my hand vac pump.

[itreflop117]

Originally Posted by PatrickGSR94

Yeah mine has the cap, and the little filter inside of it. But the bottom port no longer holds a vacuum when I stick it on my hand vac pump.

damn.. well i guess my opinion would to get a new one bro. I don't really know what to tell you. and it doesn't really have to be necessarily new.. as long as you can find a used one on ebay..

and if ebay doesn't work. you can always return it. just make sure it doesn't say AS IS or something like that. but idk. that would be my guess. good luck man.