FAQ #1 EGR Code: 71,PO401 (1 Viewer)

[landtank]

I've never had the egr code yet .

Lots of highway and 89 octane.

I'm sure I'll see it tiomorrow now

 

[Gumby]

PO401 and P0402 are all the codes for a 95 EGR system. I have all the Alldata stuff, but my printer is dead at work. When it comes back up I can print it and scan it for you. It does not translate well otherwise.

I know I have a dead VSV, I just haven't fixed it yet. I am also firmly convinced that Toyota made the system too sensitive. I have read that Honda is having a similar problem with P1457. They apparently were fined because the EVAP system was malfunctioning and not sending a code, so they made it way to sensitive. now they can't get rid of it.

 

[landtoy80]

[quote author=Junk link=board=2;threadid=10984;start=msg99435#msg99435 date=1075949808]
Now have replaced every componenet and still get P0401. Next component to be replaced is the whole pos truck.
[/quote]

You had the intake chamber off and cleaned it yet?

 

[turbocruiser]

Now have replaced every componenet and still get P0401. Next component to be replaced is the whole pos truck.

So Junk, a question please, ... you replaced every component, what was the problem??? Did you fix it or is it still a problem? The reason I ask is that I got the P0401 and using the FSM to diagnose, determined that the vacuum modulator was bad. One vacuum modulator later and I thought I was good to go ( Beowulf warned me about this, why did I make the mistake of mentioning that I "fixed" the problem, what a dumbass I am!) Anyway, today I pulled another P0401 and so I started testing some other stuff. I'm baffled...I cannot blow air through the VSV with the engine off or on idle, I also cannot get the engine to run rough at idle when applying vacuum directly to the EGR??? I thought for sure that either I would not be able to blow air through the VSV OR that I would not be able to get the engine to run rough with vacuum on the EGR. Now I'm wondering if this means that BOTH the EGR and the VSV are bad or if one of these being bad can screw up the sort of tests that I am doing to the other components? Can anyone shed some light please??? Thanks.

 

[Rookie2]

How are you trying to blow air through the VSV? I tried it by blowing (with my mouth) and about pop a blood vessle in my head, before figuring out no air was getting through. Then I tried a can of compressed air on it, and air went through. Anyways, I've go a modulator on the way.

Did you do the voltage across the terminals thing too?

R2

 

[semlin]

turbo, your note has me confused. can you or can't you get the engine to run rough at idle with direct application of vacuum to the EGR? If not then I believe that means your egr valve is bad or else the port in the intake chamber from the egr valve to the main chamber is blocked. Anyway, if it does run rough and if you have verified all the FSM vacuum tests for the modulator, then I would check every vacuum hose and metal nipple in the system for vacuum leak, blockage or oily buildup, verify there is no blockage in the EGR ports on top of the throttle body into the throttle body, then start looking at the VSV or the temp sensor.

 

[Junk]

turbo, Yeah, as mentioned, I have replaced every component at least once and most twice. The last thing, that was a few months ago now, was the valve. The old valve "LOOKED OK" but dude, I swear that since it was replaced all has been cool (note that now I am fawked since I just said that).

One issue I can not resolve though is whether or not the EGR system gets fawked during the blower install. With the supercharger, I know the vacumn does not work the way it did originally, but I can not figure out what exactly was changed. I did not keep the manual and am therefore up the creek yet again. Wish I had some magic wand, but my EGR system seems to be the maintainer of my karma.

 

[turbocruiser]

How are you trying to blow air through the VSV? I tried it by blowing (with my mouth) and about pop a blood vessle in my head, before figuring out no air was getting through. Then I tried a can of compressed air on it, and air went through. Anyways, I've go a modulator on the way.

Did you do the voltage across the terminals thing too?

R2

Well, I tried to blow the air through with my mouth and no go. I was under the impression that you should be able to blow air through this way? I did not do the voltage test yet though because I searched and saw that the voltage test can pass while the VSV fails as a result of buildup of stuff and soot so I figured that if the first and simplest test failed, no reason to go further? I'm now left wondering whether every frickin component in the system is bad...the modulator is new but both the vsv and the egr seem to test bad. I'm really stumped. Here's a question that might help me ... I even removed one of the small vacuum hoses that goes from the modulator to the intake plenum area and tried to blow through that one and could not. I think this particular hose then goes from the top of the plenum through to the bottom and then to the vsv or something else. I was wondering whether or not one should be able to blow through all these hoses with the engine off or whether some of them stay blocked and then open up during operation??? Thanks guys, this is so frustrating. OHH OHH OHH, I almost forgot, one ray of sunshine ... I asked a super trusted source ( I forgot to ask permission to share his name so I wont ) about the EGR system lowering combustion temperatures and if that matters much for a turbocharged engine, or a normally aspirated one for that matter. He told me that although it is true that the EGR when open and when introducing, or re-introducing, exhaust gas does cool down combustion temps slightly, this only occurs when the engine is under no load, no boost. Sooo although it lowers the temps slightly it does so at the exact point in time that the temps would average lowest anyways. For this reason, there is really no damage done with a faulty EGR system, it is simply an emmissions equipment thingy. Good to get it right, but not a matter of damage when driving! Whew!

 

[turbocruiser]

turbo, your note has me confused. can you or can't you get the engine to run rough at idle with direct application of vacuum to the EGR? If not then I believe that means your egr valve is bad or else the port in the intake chamber from the egr valve to the main chamber is blocked. Anyway, if it does run rough and if you have verified all the FSM vacuum tests for the modulator, then I would check every vacuum hose and metal nipple in the system for vacuum leak, blockage or oily buildup, verify there is no blockage in the EGR ports on top of the throttle body into the throttle body, then start looking at the VSV or the temp sensor.

Sem, sorry, I'm confusing myself now, and my rum and coke aint helpin eitha!!! No, so far I cannot seem to get the engine to run rough with vacuum at the EGR. I also cannot blow any air through the VSV. So either both are bad, or, one being bad affects the other's test results. So, when you say verify if there is no blockage for the EGR ports on top of the TB, what if there is, how can I clean it WITHOUT removing the intake plenum, gosh I dont wanna do that, what a PITA it looks like. Thanks all, I appreciate your advice, if you do not mind, offer any opinions or experiences.

 

[turbocruiser]

turbo, Yeah, as mentioned, I have replaced every component at least once and most twice. The last thing, that was a few months ago now, was the valve. The old valve "LOOKED OK" but dude, I swear that since it was replaced all has been cool (note that now I am fawked since I just said that).

One issue I can not resolve though is whether or not the EGR system gets fawked during the blower install. With the supercharger, I know the vacumn does not work the way it did originally, but I can not figure out what exactly was changed. I did not keep the manual and am therefore up the creek yet again. Wish I had some magic wand, but my EGR system seems to be the maintainer of my karma.

Thanks Junk, I appreciate it. I also was wondering whether or not the turbo system screws around with the EGR? Anyone know if in Australia they have EGR systems? Either way, I know that for a long long long time, I had no EGR problem so I would think that either forced induction makes no difference, OR that these systems somehow compensate for it. Let me ask if you do not mind, did you test the EGR with vacuum before you replaced it? Did it test okay but really was not, I was not able to finger that out from what was written. Thanks man, you rock.

 

[Beowulf]

>> know if in Australia they have EGR systems? <<

No EGR on the Aussie 1FZ-FE.

My engine would run very rough when vacuum was applied to the EGR valve per the FSM test.

-B-

 

[semlin]

to clean the EGR ports on the throttle body you can either pull the throttle body and clean it (4 bolts) or just pull the air bellows and clean it in situ. I used a very tiny gauge wire to ream out the ports from the outside until I saw the wire inside the tb (I used the core wire from a twist tie I stripped). You can clean the tube in the intake plenum by pulling the egr valve and the throttle body, which gives you full access. Maybe an hours work. compressed air (even the computer cleaner can) helps, as does carb cleaner or similar. You will need a pipe cleaner or similar to clean the intake chamber port.

FWIW, my EGR valve , modulator and VSV are all new, as are all the vacuum hoses, plus I had to ream out the intake plenum, and I had a blockage in the throttle body EGR ports. The only thing I did not replace was the temp sensor, because my model does not have one!

 

[turbocruiser]

to clean the EGR ports on the throttle body you can either pull the throttle body and clean it (4 bolts) or just pull the air bellows and clean it in situ. I used a very tiny gauge wire to ream out the ports from the outside until I saw the wire inside the tb (I used the core wire from a twist tie I stripped). You can clean the tube in the intake plenum by pulling the egr valve and the throttle body, which gives you full access. Maybe an hours work. compressed air (even the computer cleaner can) helps, as does carb cleaner or similar. You will need a pipe cleaner or similar to clean the intake chamber port.

Sem, thanks, that's good to know. Just to make sure I'm reading right, are you saying that there is no need to remove the intake plenum completely and clean it?

 

[semlin]

yes. if you pull the throttle body and the egr valve you can access everything.