I am new to this site and this is my first post. Before I get started, I want to point out that I am not a mechanic or a rocket scientist or a grammer/ spelling teacher. I have a general idea of how things work, but don't always know....... Most all that I have done to figure out what I have, is due to reading posts here, and my own observations.
I got the dreaded egr insuf. flow code...PO401... After finding out what the parts to the egr system cost, I figured that I would try and "fix" what I could.... I ordered the egr seal for only a couple bucks..... removed the egr valve itself and cleaned it the best I could and soaked it in carbon remover cleaner. tested by moving the piston up and down with a pair of needle nose pliars.... sucked on the vacumm line to check the diaphram . It seemed all ok and worked the way i thought it should. Next I started up the truck and checked the flow of exaust out of the tube that comes up..... seemed like it was clear of any clogs...... after deciding that it all seemed ok I put it all back together. unscrewed the temp sensor and cleaned the carbon off it and reinstalled it.... put it all back together, disconnected the battery to clear the code and started it up. drove for a day and got the code po401 again. Took it to Advanced Auto for the free code read........
after Reading meny threads on this site, I decided that i needed to check out the Vacumm Switching Valve ... or VSV. but I was a little intimidated by the process.... but after a few days of trying to come up with a plan I just decided to go with the removal of the throttle body ... I was actually suprised that it was really easy. I took some digital pics of it all together just in case..... it only took about 20 to 30 minutes to get to the vsv and remove it.... the air cleaner "tube", a few vacumm hoses, 2 small coolent hoses, 4 bolts and vvvvwala........
I had read one thread discussing moving the VSV to another place in the engine compartment . not only to provide easier acsess, but for cooler operating temp too.... thought it seems like a good idea, so I threaded the electrical wire through to where i could get to it later... ran longer vacumm hoses for the same reason.....
I tested the VSV the only way it made sence to me..... sucked on one hose and ran 12 volts across it and it didnt close..... COULD THI BE MY PROBLEM? well after coming to the conclusion that it was bad, i figured that i would take it apart to see if I could get it to work... hey, maybe it was just a little piece of carbon blocking it..... I was very suprised as to how simple this thing is.... a basic sylanoid..... an electromagnet with a rubber stopper on the end..... it was stuck in the open position.... I started thinking....
If it is stuck in the open position, air is constantly going through it....... not allowing enough sucktion to pull up the diaphram on the egr valve to open it.... SO, I pluged the hoses that came off the VSV so that it would duplicate the valve being stuck closed......... this in theory , would make the egr valve open almost all the time........ WOULD I GET THE OPPOSITE CODE THAN I WAS GETTING BEFORE? Ecsessive flow? PO402?
Three days later I got my answer.......
My check engine light came on..... ironicly 1 block away from Advanced Auto..... stopped in and in 5 minutes found out that this time I had too much air flow....... The opposite of my origional code and problem ...... I think I found my problem....
NOW.... my next question..... since I am relocating the VSV, why couldnt I use one from a different vehicle that is much less expensive? as long as it is "open" when there is no voltage , and closed when there is..........
Has anyone ever done this? I just don't have the money for the Toyota one right now....
I did get a 1k ohm resistor to fool the ecu for now.
also, I did bump the timing up to 9 deg. BTDC ...... this is a wonderful suggestion....and makes a huge differance.... thanks guys.....
I got the dreaded egr insuf. flow code...PO401... After finding out what the parts to the egr system cost, I figured that I would try and "fix" what I could.... I ordered the egr seal for only a couple bucks..... removed the egr valve itself and cleaned it the best I could and soaked it in carbon remover cleaner. tested by moving the piston up and down with a pair of needle nose pliars.... sucked on the vacumm line to check the diaphram . It seemed all ok and worked the way i thought it should. Next I started up the truck and checked the flow of exaust out of the tube that comes up..... seemed like it was clear of any clogs...... after deciding that it all seemed ok I put it all back together. unscrewed the temp sensor and cleaned the carbon off it and reinstalled it.... put it all back together, disconnected the battery to clear the code and started it up. drove for a day and got the code po401 again. Took it to Advanced Auto for the free code read........
after Reading meny threads on this site, I decided that i needed to check out the Vacumm Switching Valve ... or VSV. but I was a little intimidated by the process.... but after a few days of trying to come up with a plan I just decided to go with the removal of the throttle body ... I was actually suprised that it was really easy. I took some digital pics of it all together just in case..... it only took about 20 to 30 minutes to get to the vsv and remove it.... the air cleaner "tube", a few vacumm hoses, 2 small coolent hoses, 4 bolts and vvvvwala........
I had read one thread discussing moving the VSV to another place in the engine compartment . not only to provide easier acsess, but for cooler operating temp too.... thought it seems like a good idea, so I threaded the electrical wire through to where i could get to it later... ran longer vacumm hoses for the same reason.....
I tested the VSV the only way it made sence to me..... sucked on one hose and ran 12 volts across it and it didnt close..... COULD THI BE MY PROBLEM? well after coming to the conclusion that it was bad, i figured that i would take it apart to see if I could get it to work... hey, maybe it was just a little piece of carbon blocking it..... I was very suprised as to how simple this thing is.... a basic sylanoid..... an electromagnet with a rubber stopper on the end..... it was stuck in the open position.... I started thinking....
If it is stuck in the open position, air is constantly going through it....... not allowing enough sucktion to pull up the diaphram on the egr valve to open it.... SO, I pluged the hoses that came off the VSV so that it would duplicate the valve being stuck closed......... this in theory , would make the egr valve open almost all the time........ WOULD I GET THE OPPOSITE CODE THAN I WAS GETTING BEFORE? Ecsessive flow? PO402?
Three days later I got my answer.......
My check engine light came on..... ironicly 1 block away from Advanced Auto..... stopped in and in 5 minutes found out that this time I had too much air flow....... The opposite of my origional code and problem ...... I think I found my problem....
NOW.... my next question..... since I am relocating the VSV, why couldnt I use one from a different vehicle that is much less expensive? as long as it is "open" when there is no voltage , and closed when there is..........
Has anyone ever done this? I just don't have the money for the Toyota one right now....
I did get a 1k ohm resistor to fool the ecu for now.
also, I did bump the timing up to 9 deg. BTDC ...... this is a wonderful suggestion....and makes a huge differance.... thanks guys.....
and I would also say congrats for taking it on yourself to try and trouble shoot even with the limited resources you have. I think we can all agree that the diode is a very temporary band-aid and is only there so you dont have to stare back at a CEL while you are driving and that you are going to eventually fix it. What I would do in your case is call some of the outfits here on mud and see if you can get a used one from CCOT or SOR or take a look at the classifieds section for someone parting it out. You could get it for just a few bucks. As far as relocating it I actually talked to my own smog person about that when I saw the first post about moving it. He said he totally understands the reasoning for moving it and would not himself even second guess it so long as it looks like its in a factory location. Meaning so long as dont mount it to the firewall or inner fender where it calls attention to itself you should be fine.
(though,
they would be more help then a couple of gay guys 
) 
