9 times out of 10 a PO401 Code is fixed by . . . . . (1 Viewer)

[d0ubledown]

Boy a picture is worth 1000 words here. You are referring to a throttle body port, correct? I don't have a 1FZ-FE in my driveway. Where does the VSV live?

have a look at the pic super90 posted. that vacuum port im referring to is the one circled in blue. it goes through the plenums, but not into the intake directly. its just a tunnel. its connects to the VSV, which lives underneath the rear 3 intake runners. you can barely see it when looking over the DS fender, under the intake tubes.

 

[NorCalDoug]

don't mind me...just subscribing to another P0401/VSV thread...

 

[jonheld]

Thanks for the picture Robert. Understood.
Sonny, I'll see what I can find next time I get a chance to look at the truck.

Thanks to you both.

 

[corbinwelter]

so my cruiser just threw a p0401 code, when i replaced the HG, i noticed the port that goes through the intake from the VSV to the EGR was clogged and i could not get it cleaned out it was so clogged. so i bypassed it with a tube going under the intake, around, and up to the top to the EGR port.
will this be ok? or could it be throwing the code?

 

[NorCalDoug]

so my cruiser just threw a p0401 code, when i replaced the HG, i noticed the port that goes through the intake from the VSV to the EGR was clogged and i could not get it cleaned out it was so clogged. so i bypassed it with a tube going under the intake, around, and up to the top to the EGR port.
will this be ok? or could it be throwing the code?

...okay...so, now I sorta feel dumb cuz I didn't think of doing that when I replaced my VSV...
I can't think of a reason why that would be throwing the p0401 code. Did you use oem Toyota vacuum hoses?

 

[d0ubledown]

so my cruiser just threw a p0401 code, when i replaced the HG, i noticed the port that goes through the intake from the VSV to the EGR was clogged and i could not get it cleaned out it was so clogged. so i bypassed it with a tube going under the intake, around, and up to the top to the EGR port.
will this be ok? or could it be throwing the code?

it shouldnt. did you replace the VSV when you did the HG? usually the VSV is the culprit. theres a way to test whether or not its functioning properly. also did you do the modulator tests?

 

[AJP]

a new vsv for egr fixed my PO 401

 

[alia176]

so my cruiser just threw a p0401 code, when i replaced the HG, i noticed the port that goes through the intake from the VSV to the EGR was clogged and i could not get it cleaned out it was so clogged. so i bypassed it with a tube going under the intake, around, and up to the top to the EGR port.
will this be ok? or could it be throwing the code?

That should be fine as it's doing the same thing functionally. However, did you use the Toyota metric size hose for this bypass? I've found that non Toy hoses don't slip fit tightly over the nipples (damn, that sounds kinda kinky).

 

[Pateras]

Plugs, wires, cap and rotor just fixed mine.

 

[NorCalDoug]

Plugs, wires, cap and rotor just fixed mine.

That fixed the P0401?

 

[Flank]

Plugs, wires, cap and rotor just fixed mine.

Funny, I did not think the P0401 had anything to do with ANY of that...

 

[95Fantasma80]

Tagged... my plan is to clean the port, replace vacuum lines and the modular... hope it works.

 

[33tab]

I chased mine around for a year. I even had a vacuum gauge on my dash for six months and verified the VSV function with the Scan Gauge II. Still couldn't figure it out. A few months ago I discovered that the port in the intake manifold that is circled in red was the first culprit. I cleaned it out thinking I had discovered Shangra La but the pesky PO401 came back again. I started checking vacuum on all lines again since I've had the Vacuum gauge off of my dash for several months and realized that it was no longer working as it was before. I discovered that I had no vacuum from one of the ports on the throttle body. I then realized that at some point a pin hole had developed in modulator valve and the constant flow of exhaust gases back to the port had caused the clog. I replaced the modulator valve and cleaned out the port. Scan Gauge II now reads No Codes Found "Ready!" Yipee!!!!

The local dealer had replaced every part in the system for the PO at 120,000mi at a charge of >$1000 and the problem was back in <10,000mi.

The only problem now is that my fuel mileage dropped by 1-2mpg.

 

[landcruiser3DP]

have a look at the pic super90 posted. that vacuum port im referring to is the one circled in blue. it goes through the plenums, but not into the intake directly. its just a tunnel. its connects to the VSV, which lives underneath the rear 3 intake runners. you can barely see it when looking over the DS fender, under the intake tubes.

old thread. persistent code.

any chance of getting a pic of these two passages that need to be cleaned?

links seem busted.

THANKS

 

[MoJ]

Follow the troubleshooting steps in the FSM.

 

[landcruiser3DP]

Follow the troubleshooting steps in the FSM.

thanks...

 

[landcruiser3DP]

I think there is some confusion. Back in post #2, I was talking about the port that is cast into the intake, is the better part of an inch in diameter and that runs from the EGR valve, toward the front of the truck, and ends just to the right of the throttle body as one looks into the engine bay. (Circled in red and I'll call it the "red port")

Other folks seem to have had problems with the port to the vacuum line that is molded in between a couple of the intake runners. (Circled in blue) I don't have any experience with that.

In my case, the red port was clogged with carbon where it opens up into the top of the intake just aft of the throttle body. That is where I am recommending folks look early on in their troubleshooting, as it is cheap, easy and is a frequent culprit. Again, an ex-Lexus "wrench" said that on the LX450's this was their first stop in troubleshooting the code.

Hope this clears things up !

anyone happen to have a pic showing the “red port” and “blue port” in this post?

 

[landcruiser3DP]

<snip> IMHO the fact that this port runs through the intake is one of the great mysteries of Toyota design. It had to be expensive to put the ports on and run the line through the intake instead of just running a vac hose or even a SS hard line over the top of it. So, they were trying to accomplish something... but what/why?

so...

has anyone taken a length or two of vacuum hose and seen if this clears the code?

i mean, i’m tempted to do this (if it is even possible) as long as i have some with some adult supervision...

<edit: i guess @corbinwelter already did this with no problems - which is probably why i asked...>