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

[SeanAndHis80]

Who cares what the condition is? Just replace all of the vacuum lines. Why wouldn't you? They're cheap and they're all accessible without removing the intake! I've got fresh rubber throughout.


Haha, but there is a need to remove the upper intake!?



Remove 4 bolts / loosen 1. That's all it takes to check your EGR bits.

Not with my large hands. You must be dexterous to have gotten to and replaced all of the hoses under there without seeing them - congrats. No way was the VSV coming out w/o splitting the plenum for me - but none the less checking it was simple w/o removing it ...like 5 minutes simple and outlined in the FSM.

 

[MoJ]

Unless you really just want to take the upper plenum off there's no need to when replacing the VSV or fuel filter. The VSV comes out from below with a few long extensions. The fuel filter is a piece of cake with the DS tire off.

 

[alia176]

If you guys remove the upper plenum brace (goes from the top to the bottom, near the oil pan), this will give you more wiggle room.

For more pics on this, search for the "external VSV mod" by Kenton and you'll get some more ideas. Placing the VSV outside by using longer vacuum hoses will help you guys with your P401 chase game!

 

[super90]

does toyota sell the proper vacuum hose per foot? i recall reading the size was an oddball one. anyone know the prope size ID/OD of the vacuum lines? will probably get some from the parts store instead of the stealership...

Best to buy the Toyota stuff. I tried sourcing an aftermarket vacuum line when I had my FJ60, all to no avail. The FZJ hardly has any vacuum line in comparison. Call CDan. It isn't that expensive. It comes in metric lengths and I think I bought something that was almost a meter long most recently It wasn't enough to do everything. Probably need twice that.

 

[super90]

thanks for the heads up. ill probably end up pulling the intake off, since i also have a new fuel filter thats been sitting for a year waiting to go in. access to the vsv hoses as well...and i'll do a thorough cleaning of the TB and intake plenums. i hate having scratched up hands trying to shoehorn them into tight places...doing the PHH was bad enough....

Too bad you already did the PHH as it's really easy with the top of the intake off.

Cleaning the top of the intake is a good idea, but I couldn't find a way to clean the bottom without risking having all sorts of cleaner drain down into the valves and cylinders potentially causing a big problem. Liquids don't compress so well ! So I just wiped them a bit and left that alone.

Also, might pull the injectors for servicing while this is all apart. That's what I did and am very happy to have gone the extra mile. Just find a local diesel injection shop. They will have an ultrasonic cleaner and can flow test them. I paid $25 each, which included o-rings. Same day service.

 

[kpoon]

Once the EGR problem is fixed, do you need to manually reset the MIL?

At this point I've replaced the VSV & the EGR Vacuum Modulator, & I've also cleaned out the port that runs through the intake. The port was clogged with carbon, & I used a 1/16" x 12" aircraft drill bit to clear it out.

Once the EGR problem is fixed, do you need to manually reset the MIL, or should it clear by itself after a few drives?

After fixing everything, I took the LX450 out for a test drive. I hit >50 mph, parked & stopped the engine, then hit >50 mph again. But the MIL is still lit.

 

[retrofive]

IIRC after a few cycles ti should clear itself. That being said, I was never that patient and just pulled the EFI fuse to clear and see what would happen.

 

[super90]

Or, disconnect the battery for a minute or two and reconnect. That will reset the computer. That's what I always did.

If that port was totally clogged, I bet that was what was throwing the code. It was on my rig.

 

[kpoon]

IIRC after a few cycles ti should clear itself. That being said, I was never that patient and just pulled the EFI fuse to clear and see what would happen.

My CEL/MIL finally went out on my drive into work. Hallelujah! After 2 years of the dang thing staring me in the face, it finally went out! Gonna call today to make an appointment for my (overdue) emissions inspection. Thanks to everyone here on the forum for their advice & input.

 

[40cruise]

I've had my 40th since April and CEL was on. Code 401. I was so used to it being on I just ignored it until I could diagnose every EGR component. 3 weeks ago, I ordered parts from Dan for a complete tune up, that included new wires,plugs,rotor, pvc, fuel filter,air filter and oil change. After tune up, I drove about 300 miles to Marthas Vineyard. CEL was still on all the way up there. When I stopped to refill on the island and started my cruiser back up...Low and behold the CEL was out. It remained off for the return trip a week later and is still off. I don't know what caused mine to finally go out but I'm in about 500 miles and no CEL.

Go Figure...I will see how long this last. but so far so good

 

[dgspencer]

My CEL's been on since I got my '94 about 50K miles ago. I just fixed it a couple of months ago. EGR port was clogged so cleaned that up good. VSV for EGR tested bad, so replaced it. It was pretty clogged up, so I think I had the dual problem. Who cares, no more CEL. Replaced all vacuum hoses on engine, and coolant hoses, as I drove about 5,000 miles around the northwest this summer. When I fired it up after the work, I asked my son if it didn't sound smooth, and he said no, it sounds raspy. Shortly after, the EGR closed, and that motor hummed smoother than it ever has since in got it.

Some older threads have suggested no MPG improvement, which has NOT been my experience. First trip after fixing it, I got 18 MPG from Boise to Sun Valley, 61 MPH and no air. I don't think I've ever gotten 14 MPG in this truck, average about 11.5. On my long trip through Oregon, I got 13-14 towing a large tent trailer with the air on most of the time, at much higher speeds than optimum. Previously I'd get 9-10 MPG in those conditions. Most recent trip got 13-16 with air on at high speeds, would have been 10-12 before.

Wish I'd have done that fix long ago.

 

[aktundra]

Finally have some time to deal with the P401.

Looks like it is the VSV controlling the EGR.

The FSM calls out removing the intake air box. Which requires draining the coolant and it looks like removing 24 connections to the air box !

Does anybody have a good pic of the EGR VSV with the air intake box removed so I can see if perhaps I can just remove the intake manifold strap and reach in a jimmy the switch out ?

 

[mikesean76]

Finally have some time to deal with the P401.

Looks like it is the VSV controlling the EGR.

The FSM calls out removing the intake air box. Which requires draining the coolant and it looks like removing 24 connections to the air box !

Does anybody have a good pic of the EGR VSV with the air intake box removed so I can see if perhaps I can just remove the intake manifold strap and reach in a jimmy the switch out ?

Try this:

https://forum.ih8mud.com/80-series-tech/203948-replacement-vsv-spanish.html

 

[aktundra]

OH MY GOODNESS !!!!

mikesean76 . . . . .what an awsome thread.

honestly, the FSM had 24 steps, replacing gaskets, and dis-connecting almost everything on the intake manifold.

It took longer to put back the stuff I had started, than to follow the process in the link.

DD back on the road after a couple of hours, Thanks.

 

[Bluetribal]

My 401 has been defeated for almost two months now and passed smog no problems.... Testing all three items; VSV, VSV for EGR & Vacuum Valve showed that I needed to replace both the VSV for EGR & Vacuum Valve. A call to CDan, another weekend replacing the two parts I had already pulled to test before and disconnecting the battery cable and I haven't seen the engine light since.
To the board, CDan, & to LandCrusher'70 for walking myself and two other MUD members through the underside process.

 

[Houston FZJ80]

Replacing all the seals and head gasket on my motor right now... needless to say, everything is apart... I too had a 401 bugging me for over a year. The passage through the intake was completely blocked and several hoses under the intake were dry and cracking.

If anyone wants detailed photos of anything while it is apart...

Check the passage first. It may be as simple as that.

 

[jonheld]

A little 1FZ-FE help please

I cleaned the little vacuum port that goes into the intake with a piece of stiff wire. I thought it went into the intake, but it actually goes THRU the intake, so use a long piece of wire, and disconnect the hose connected to the other end of the port under/inside the intake (sort of hard to access) before you start cleaning. I cracked the flux off a piece of 7018 welding rod and used it to clean with, because it is stiff and straight. I used a drill bit first, before I realized how long the vacuum port tube was. For me, this was the fix. Have not had a PO401 in the 2 years since. If I had tried this first, I would have fixed it for free. Instead, I have a nice supply of back-up parts should either of them fail (for $138 )

My brother's 97 LX450 has been throwing this code. Last week we replaced all vacuum lines, cleared the code and it re-appeared. The above quote from Livinoffroad mentions a vac port. As I am somewhat unfamiliar with the 1FZ-FE, can someone show me a picture of what port you guys are all talking about?

I know the EGR lives in the rear of the intake as opposed to the left side on a 3FE. Is the second flying saucer called the vacuum modulator as well? Aha. Yes it is called the vacuum modulator. Thank you EPC.

 

[d0ubledown]

that port that everyone referrs to is the on that goes from the egr to the VSV for egr. it goes through the last couple intake runners (#5 & 6 i think), and connects through to the vsv. it is often clogged up with carbon. a silly way to route vacuum really, not sure why toyota designed it that way. i think the egr was an afterthought, and not well routed. under the intake plenums gets very hot...and is not the most suitable place for putting a vsv. vacuum tubes get hot, dry out and crack.

ive had my P0401 for just over a year now. not too worried about it, since ive got a workaround for passing our yearly smog tests. one of these days, i'll replace the VSV as ive tested my modulator and it seems to work as it should. its just a PITA to do the VSV. you can either go the easy & quick way, from underneath, or the more involved process of taking off the upper intake tubes. this way allows you to clean out the TB since its out, and the fuel filter which ive also got waiting to be replaced. some have also had good luck getting to the vsv just by removing the TB, and going through the side & underneath...

 

[jonheld]

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?

 

[super90]

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 !