are there 2 Vacuum switching valves on an 80 / LXX450? P0401 problem (1 Viewer)

[goneballistic]

I'm in the middle of trying to fix an ongoing P0401 on my 1996 LX450.

before I go on, I would like to humbly request that if anyone knows someone who work at Toyota who helped design and locate the EGR pieces on the LX450, please, hit them in the face with a shovel for me.

I've only seen this stupid of engineering once before in my life, on an Oldsmobile, and that's debatable.

I am following the outstanding thread posted by cahill found here : PO401 and EGR/air intake manifold with pictures

I am looking at the bottom of the manifold which looks like this:

I have replace a vacuum switching valve which is labeled #1 in this picture, that's replaced.

I also found a completely blocked vacuum hose connection into the manifold which I cleared

but notice in this picture, towards the bottom just south of the number 3, and behind the black hose that has the text "HOSE#" on it, there is a little brown thing showing.

It looks EXACTLY like the vacuum switching valve that threw a P0401 on my 2001 Toyota Camry. I looked at the part number on the part an it's this thing:

a Toyota Vacuum Switching valve. Part number
Toyota 90910-12043

https://www.amazon.com/Genuine-Toyota-90910-12043-Vacuum-Switch/dp/B00GJJKS9E

So my question is: do I need to replace this one too? I am going to be pissed if I put this thing back together and then have to take it apart again.

the part is 95 bucks so preemptively replacing it will sorta hurt, but it would be better than having to tear the manifold off again.


none of the threads I've read have mentioned this part, so I am not sure if I should replace it or not.


Any thoughts? I wonder if I could test this easily by jumping 12 volts to one of the pins and seeing if anything happens.

 

[-Spike-]

I'd be testing it. Put a vaccuum pump on it if you have one, see if it holds, see if it releases (or vice versa). Or just suck it.

 

[goneballistic]

I'd be testing it. Put a vaccuum pump on it if you have one, see if it holds, see if it releases (or vice versa). Or just suck it.

<-- That's what she said



based on a generic VSV test I found, I put pressure on the middle port, and air comes out the bottom port, then I applied 12V and it clicks and air then vents out the little round vent thing at the top.


so I think it's working as designed. I'm going to reinstall this dang thing, hating the engineer who decided to put this mess UNDER the manifold the entire time, and hope for the best.


stay tuned, if this fails and I have to pull it down again the meltdown is gonna be epic.

 

[-Spike-]

At least the starter isn't under there too...

 

[Malleus]

x2 for the shovel.

 

[ajax1]

I just took all that stuff out and threw it in box in the garage and put jumper in the egr harness

 

[Dubbinchris]

You should see the underside of the IM on my Audi A4.....very similar.

 

[80t0ylc]

I just took all that stuff out and threw it in box in the garage and put jumper in the egr harness

Can you expound on this? What year is your rig? Might want to try it.

 

[madisonr34]

My advice:
Don't use any of the hard intake manifold hose connections. Just by pass all of them and run straight hose to each vsv and the egr valve.
This the replacement vsv I used. Works like magic. Way cheaper too.
The 2nd VSV you mentioned goes to the fuel canister and won't cause the error code.

 

[ajax1]

Can you expound on this? What year is your rig? Might want to try it.

I have obd1 94, I do not have the pair system, ran o2s where that bolts into manifold. Plugged the air canister where it feed the pair. Egr has jumper wire in the harness, sensor is just unplugged. Capped off all vacuum lines except one for the fuel pressure regulator. Charcoal canister one line from tank left alone, the line that feeds the vsv goes out the wheel well just like the stock can. I have no codes and truck runs and idles great. Been that way for years now. I can post some pics later if you like

 

[Tools R Us]

On an OBD2 rig, this can be solved by a 4.7K ohm resister, and two .110" spades, replacing the thermistor.

 

[80t0ylc]

I have obd1 94, I do not have the pair system, ran o2s where that bolts into manifold. Plugged the air canister where it feed the pair. Egr has jumper wire in the harness, sensor is just unplugged. Capped off all vacuum lines except one for the fuel pressure regulator. Charcoal canister one line from tank left alone, the line that feeds the vsv goes out the wheel well just like the stock can. I have no codes and truck runs and idles great. Been that way for years now. I can post some pics later if you like

Mine's a '94 also. I'll have to remove the pair on mine. Not sure what you mean "ran o2s", but I remember it bolting to manifold. So a pic of that might help. Then unplug egr sensor wire, right? Remove and cap all vacuum lines except fuel pressure regulator & charcoal canister. Does that eliminate all the BS mess under intake manifold except for a single vsv for charcoal canister? I'm asking because I haven't looked at this on my rig yet - going off my fading memory...lol.... Btw, thanks for your help!

 

[ajax1]

Mine's a '94 also. I'll have to remove the pair on mine. Not sure what you mean "ran o2s", but I remember it bolting to manifold. So a pic of that might help. Then unplug egr sensor wire, right? Remove and cap all vacuum lines except fuel pressure regulator & charcoal canister. Does that eliminate all the BS mess under intake manifold except for a single vsv for charcoal canister? I'm asking because I haven't looked at this on my rig yet - going off my fading memory...lol.... Btw, thanks for your help!

Yes but I also do not run the vsv for the fuel, yes my o2 sensors are in manifold. Unplug egr temp sensor then out the jumper on the engine harness side, then either block off and remove egr or loop the vacuum lines off it. This will eliminate all but one vacuum line and all the mess under the intake, on the plug that is plastic under the manifold that screws into the block I just loop those two ports or block them off with plugs

 

[80t0ylc]

Thanks! Weather sucks here today. I'll check it out later.

 

[80t0ylc]

Yes but I also do not run the vsv for the fuel, yes my o2 sensors are in manifold. Unplug egr temp sensor then out the jumper on the engine harness side, then either block off and remove egr or loop the vacuum lines off it. This will eliminate all but one vacuum line and all the mess under the intake, on the plug that is plastic under the manifold that screws into the block I just loop those two ports or block them off with plugs

I might just put plugs in the manifold & keep my existing o2 sensors where they are. Shouldn't be a problem, should it?

 

[ajax1]

You prob be ok I left old o2s in the exhaust and put new ones into the manifold

 

[goneballistic]

I just took all that stuff out and threw it in box in the garage and put jumper in the egr harness

I wish I would have just done this lol. I don't understand the system well enough to know how to jumper the harness in the right place to clear the CEL. I would have caused a no start or a fire or something dumb.

I tested the other VSV, it was fine. I wish I would have used the Dorman valve but I had already ordered a toyota VSV.

got it all back together, which was a total PITA. First cause I dropped the EGR gasket into the engine about five times, second, cause I failed to reconnect a vacuum hose under the intake before I installed it, causing me to remove the throttle body again after it was altogether.

my neighbors are still crossing the street before walking past my house after that outbreak....


fired it up and drove it about 30 miles, no CEL so far. So fingers crossed!

 

[-Spike-]

I had the same code, clearing the manifold vacuum passage fixed it as well. Bypassing it would be easy, which is what I'll probably do if it gets obstructed again.

 

[Hollis Cameron]

I'm in the middle of trying to fix an ongoing P0401 on my 1996 LX450.

before I go on, I would like to humbly request that if anyone knows someone who work at Toyota who helped design and locate the EGR pieces on the LX450, please, hit them in the face with a shovel for me.

I've only seen this stupid of engineering once before in my life, on an Oldsmobile, and that's debatable.

I am following the outstanding thread posted by cahill found here : PO401 and EGR/air intake manifold with pictures

I am looking at the bottom of the manifold which looks like this:

I have replace a vacuum switching valve which is labeled #1 in this picture, that's replaced.

I also found a completely blocked vacuum hose connection into the manifold which I cleared

but notice in this picture, towards the bottom just south of the number 3, and behind the black hose that has the text "HOSE#" on it, there is a little brown thing showing.

It looks EXACTLY like the vacuum switching valve that threw a P0401 on my 2001 Toyota Camry. I looked at the part number on the part an it's this thing:

a Toyota Vacuum Switching valve. Part number
Toyota 90910-12043

https://www.amazon.com/Genuine-Toyota-90910-12043-Vacuum-Switch/dp/B00GJJKS9E

So my question is: do I need to replace this one too? I am going to be pissed if I put this thing back together and then have to take it apart again.

the part is 95 bucks so preemptively replacing it will sorta hurt, but it would be better than having to tear the manifold off again.


none of the threads I've read have mentioned this part, so I am not sure if I should replace it or not.


Any thoughts? I wonder if I could test this easily by jumping 12 volts to one of the pins and seeing if anything happens.

What's #3 in your image?

 

[cahill]

What's #3 in your image?

It is the check valve for evap. If you click on the link he posted the numbers in each picture are explained in the post.