testing EGR modulator - Toyota Nation Forum : Toyota Car and Truck Forums

ryan4321 · 11-15-2010, 12:37 PM

Is it possible to test this part by blowing into it with my mouth? My Hayne's manual says I should be able to cover P and R with my finger, and blow into Q. It says air should pass "freely" through. The illustration seems to depict air coming out the sides of the modulator. I tried this using my mouth to blow the air and very little if any would pass through. It definitely didn't pass through "freely". This was about 90 minutes after driving, with all engine parts cool or luke warm.

I have the P0401 code and changed the EGR valve itself, but that didn't help. I have read here that it is usually the VSV that is the problem, but the modulator is so easy to get to and change, I want to rule out a problem there first.

-Ryan

Nervous · 11-15-2010, 01:20 PM

Check this thread and especially read PDF docs (links are in the first post):
DIY: 1MZ, EGR, code P0401 & P0402 diagnostic & repair

ryan4321 · 11-15-2010, 02:11 PM

Thanks Nervous. Some background: I changed my EGR valve before I realized there could be other causes for P0401. I'm not an experienced mechanic, but managed to change the EGR valve.

I unplugged the battery to reset the code, but it came back after a few days. So today I went to autozone to get the code read. Same P0401 code. Which leads me to this point of changing either the VSV or modulator (or both, I suppose). And thus I want to test the modulator since it is so very easy to get to.

The PDF articles look good but are somewhat technical for me and involve some tools I don't have. I wish I knew someone else with a camry so I could pop off the modulator and just blow in it to see if it passes air better than mine. Mine does pass some air but not "freely".

I guess I could play the percentages, as one of the articles suggests, and just change the VSV. I just feel like even if I had all the tools to do the testing (renting from Autozone or whatever) that I might get confused and do the testing wrong.

ryan4321 · 11-16-2010, 10:49 AM

I also found this *great* thread that has lots of detail about changing the VSV:
http://www.tundrasolutions.com/forum...2-2l-2001-vsv/

coffee-3000 · 11-26-2010, 11:22 PM

Were you able to resolve your issue ? Did you replace the EGR modulator or the VSV ? Let me know if you want me to try the Haynes Manual test on my EGR Modulator to see if air passes through freely.