EGR 401 error, VSV is new, but still not working

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RyRoRyan

RyRoRyan

Joined
Jan 26, 2017
Threads
24
Messages
133
Location
Albuquerque, NM
I have a new to me LX450. Had a 401 when I got it. The PO just changed out the VSV thinking that might be the cause. With it being out and exposed now, it helped me diagnose a little bit. EGR works fine if I draw vacuum on it directly (engine stalls). I ohm the VSV and get ~36 which is about right. I hook it all up and touch the VSV with my hand and have my son rev the engine up to about 2800 RPM. The VSV never clicks. So I disconnected the connector at the VSV and put a multimeter on it and tested for voltage when reved up. Sitting at idle I get about .15 volts. Reved up I get about .36 volts. That for sure is not 12v. So I may either have a bad connection, bad ECU (SUCKY), or I may not be calling the signal correctly to tell the system to turn it on. I dont have a high end scan gauge so I cant take control of various systems and just tell the VSV to turn on. I do have the FSM, so I can see that power to the VSV comes from what appears is the EFI main relay and the ECU, but I dont know where or how to test those. I assume that since it starts up, the EFI relay works. Should one of those VSV wires, go directly to ground, or is this one of those, it lifts the ground to separate the connection and positive is always connected via the relay or something. It somewhat appears this way with the wiring diagram, unless I am reading it wrong, as I assume the EFI relay powers more than just the VSV valve. Can anyone help me figure out where I need to go next with this? I live in a smog county and I cant get this thing registered until I get this figured out.
 
Are you certain it is an OEM VSV?
 
Hmm. I just order a VSV for myself :doh:. So my advice is useless right now. But I knew my modulator was bad when no air would pass through it in any direction and large puffs of dust came out of the filters :confused:.
 
Under what conditions does the vsv open the egr valve?

I'm prerty sure the motor need be at operating temp and not under load for vsv to open and apply vacuum to the egr valve.
The fsm might call it cruising conditions or something. I thought I read that in the book but maybe 2 years ago so......
 
So to make sure I am not barking up the wrong tree...does anyone know the exact conditions needed to turn the VSV on? I have verified that +12v exists to the unit using body ground. And have confirmed that yes it does get power by the ECU using the ground. I doubt the ECU is bad, but it would not be the first ECU I have replaced in a car if it is. Something just tells me that I just don't have the right conditions to turn it on. I really wish I had an OBD that had mode 8 on it right now, so I could just force it.
 
If you're not OBDII, just remove it all and block off the egr port. You don't need any of that garbage going back in your engine, anyhow!
 
Ok...think I got it figured out. His shop told the PO that it was not the modulator that was causing the problem, as they checked it. They replaced the VSV thinking that was the problem. Because I thought (shame on me) to trust the shop, I skipped over the modulator tests. Well, I figured that I might as well do it since I am in there. Low and behold, put a vacuum gauge up to the output and reved the engine and got nothing. Boom, that's a big problem. Took the input hoses off and tested those. Got really good on P, but very little on R, like barely moved the gauge. Cleared R out and got a better reading...P is still stronger and it should be based off other threads I have read. Put it back together and still nothing. I disconnected the exhaust pressure side and I was getting engine exhaust pressure out the tube so confirmed I am good there. So I took the entire modulator out and then blue into P, that was stopped. Blew into Q, stopped as well. Ok I know the valve between P and Q is closed, which at rest it should be. So then I blew into the bottom exhaust port. It should move the diaphragm and then pressurize. Well instead of doing that, it came out of port R, which should be the negative side of the diaphragm. So what this tells me is that I have a hole or tear in the diaphragm and the exhaust pressure is going through it and then being sucked via vacuum into port R (which is prob why it was blocked in the first place) and into the intake but not doing it with enough volume to move the diaphragm and open the valve between P and Q. So since I need this part asap, I will call American Toyota in the morning and compare their price with the mud discount (thanks cdan) with the chain stores and grab the best unit I can if the cost is reasonable.
 
You can still delete it, but you'll have to research the resistor needed for the air temp circuit (tricks the computer to thinking its working).

It's a worthwhile mod.
 
I have a complete egr/vsv that I romped from my engine. All in perfect working condition. I can box it up and ship it if you are interested?
 
On the ones that we have fought, its most often the modulator and that causes other parts to fail. It has a diaphragm that senses exhaust pressure, when it fails, exhaust goes throughout the vacuum side, clogging it up. Dirty filter, sticky VSV, clogged vacuum lines can all be caused by this. My first test is to remove the modulator and blow in the lower port, if it doesn't hold pressure, the diaphragm is bad.

80proof said:
You can still delete it, but you'll have to research the resistor needed for the air temp circuit (tricks the computer to thinking its working).

It's a worthwhile mod.
Click to expand...

Agree, simple, problem solved, 4.7K resister. If you do this, its still a good idea to plug the lower hose at the modulator, so if(when) the diaphragm is(goes) bad, its not sucking exhaust into the intake.
 
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