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poolelx450

Vsv Function

8 posts in this topic

I am reading all of the posts discussing the possible reasons for P0401. i am getting the code consistently on my 97 lx450 after the vehicle warms up and I am cruising along at 2000-3000 rpms. I see that a lot of people fix the problem when replacing the VSV. A mechanic told me he did a test and it appears to be my EGR valve (but he is not a Lexus specialist). After studying the function of the VSV, and seeing that it is either on or off, I figured I could test whether or not it was functioning by plugging the line between the VSV and the EGR, simulating a positive condition. (my resource indicated that a negative condition would provide an atmospheric bleed, disabling the EGR). If the function of the VSV is to allow the vacuum from the modulator to activate the EGR, then my test makes sense, but if the VSV provides a vacuum itself, it is not a good test. Does anyone know whether or not the VSV provides a vacuum? By the way, after pluggint the line from the EGr to the VSV, I still got the code, which would indicate it is not the VSV.

Thoughts?

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Not sure, but I'm guessing it's just a valve that opens and closes.

Here's a summary of the testing procedure in the FSM for the VSV (get out your ohmmeter):

Disconnect both hoses.

A. Inspect for open circuit (continuity)

B. Inspect for ground

C. Inspect for operation... air flows from pipe G (horizontal pipe) to pipe E (vertical pipe). Apply voltage across terminals and check that air does not flow from pipe G to pipe E.

If operation not as specified, replace VSV.

If your CEL is intermittent, it may be that the testing procedure does not produce failing results. The procedure above is just a summary, I recommend getting the FSM so you have everything you need to diagnose. You can subscribe and download the entire FSM and more from techinfo.toyota.com. If I recall the subscription is like $10 for a day.... need a little time and computer space if you're going download a lot, cause all the sections are individual files.

Rookie.

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Not sure, but I'm guessing it's just a valve that opens and closes.

Here's a summary of the testing procedure in the FSM for the VSV (get out your ohmmeter):

Disconnect both hoses.

A. Inspect for open circuit (continuity)

B. Inspect for ground

C. Inspect for operation... air flows from pipe G (horizontal pipe) to pipe E (vertical pipe). Apply voltage across terminals and check that air does not flow from pipe G to pipe E.

If operation not as specified, replace VSV.

If your CEL is intermittent, it may be that the testing procedure does not produce failing results. The procedure above is just a summary, I recommend getting the FSM so you have everything you need to diagnose. You can subscribe and download the entire FSM and more from techinfo.toyota.com. If I recall the subscription is like $10 for a day.... need a little time and computer space if you're going download a lot, cause all the sections are individual files.

Rookie.

Thanks....This helps! The CEL is pretty consistent. I have to drive 5-10 miles after warm-up, but the CEL (P0401) comes on every time and does not go away until I reset it with my code reader. I will have to take a closer look at the VSV. If I recall correctly, pipe G(horizontal) is the one that goes to the EGR valve, and pipe E (Vertical) loops up and hooks to the bottom of the intake? That is what confused me....it would seem if there is no voltage applied, it would open the valve which would create passage from the underside of the intake to the EGR...but I could be wrong... I have no other symptoms (no roughness, no pinging, etc). I am thinking about removing the EGR and cleaning real well...could just be restricted flow from 178K miles.

I will definately look into the FSM...I can usually get to the bottom of things with the right information. I enjoy a good challenge, and I am cheap...so throwing parts at it is not my style.

Thanks again...Barry

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Thanks....This helps! The CEL is pretty consistent. I have to drive 5-10 miles after warm-up, but the CEL (P0401) comes on every time and does not go away until I reset it with my code reader. I will have to take a closer look at the VSV. If I recall correctly, pipe G(horizontal) is the one that goes to the EGR valve, and pipe E (Vertical) loops up and hooks to the bottom of the intake? That is what confused me....it would seem if there is no voltage applied, it would open the valve which would create passage from the underside of the intake to the EGR...but I could be wrong... I have no other symptoms (no roughness, no pinging, etc). I am thinking about removing the EGR and cleaning real well...could just be restricted flow from 178K miles.

I will definately look into the FSM...I can usually get to the bottom of things with the right information. I enjoy a good challenge, and I am cheap...so throwing parts at it is not my style.

Thanks again...Barry

It's been a while since I removed and replaced the vsv, so I can't remember where the hoses go. The picture in the FSM shows it pretty clearly. I'm pretty much a tight wad too and hunted around for an FSM hard copy on the cheap for a couple of months before I came across a discount source. Best $70 I've spent. This thing has it all. But for $10, access to a quick computer and about a half a day, you could download the entire FSM, Electrical wire diagram book, New car features manual (has a lot of good info. on the motor and how it's setup) and some other stuff. I just didn't know about this route when I bought mine. If you're going to do your own maitenance, it's good cheap way to get mountain of info. on these rigs.

:cheers:

Rookie

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Thanks....This helps! The CEL is pretty consistent. I have to drive 5-10 miles after warm-up, but the CEL (P0401) comes on every time and does not go away until I reset it with my code reader. I will have to take a closer look at the VSV. If I recall correctly, pipe G(horizontal) is the one that goes to the EGR valve, and pipe E (Vertical) loops up and hooks to the bottom of the intake? That is what confused me....it would seem if there is no voltage applied, it would open the valve which would create passage from the underside of the intake to the EGR...but I could be wrong... I have no other symptoms (no roughness, no pinging, etc). I am thinking about removing the EGR and cleaning real well...could just be restricted flow from 178K miles.

I will definately look into the FSM...I can usually get to the bottom of things with the right information. I enjoy a good challenge, and I am cheap...so throwing parts at it is not my style.

Thanks again...Barry

It's been a while since I removed and replaced the vsv, so I can't remember where the hoses go. The picture in the FSM shows it pretty clearly. I'm pretty much a tight wad too and hunted around for an FSM hard copy on the cheap for a couple of months before I came across a discount source. Best $70 I've spent. This thing has it all. But for $10, access to a quick computer and about a half a day, you could download the entire FSM, Electrical wire diagram book, New car features manual (has a lot of good info. on the motor and how it's setup) and some other stuff. I just didn't know about this route when I bought mine. If you're going to do your own maitenance, it's good cheap way to get mountain of info. on these rigs.

:cheers:

Rookie

I will definately go the download route....but will wait 'til I am home with high speed. Hotel room speeds may slow the download process!

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I will definately go the download route....but will wait 'til I am home with high speed. Hotel room speeds may slow the download process!

Don't know how good you are a computer stuff, but these guys worked out a pretty good routine to automate the download and speed up the process. Check out this thread:

http://forum.ih8mud.com/showthread.php?t=6...ht=fsm+download

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I will definately go the download route....but will wait 'til I am home with high speed. Hotel room speeds may slow the download process!

Don't know how good you are a computer stuff, but these guys worked out a pretty good routine to automate the download and speed up the process. Check out this thread:

http://forum.ih8mud.com/showthread.php?t=6...ht=fsm+download

I have a computer science degree (1983)...but this looks nothing like Fortran on punched cards! :blink: I am a lowly Windows XP user now...

I will definately go the download route....but will wait 'til I am home with high speed. Hotel room speeds may slow the download process!

Don't know how good you are a computer stuff, but these guys worked out a pretty good routine to automate the download and speed up the process. Check out this thread:

http://forum.ih8mud.com/showthread.php?t=6...ht=fsm+download

I did find a couple of helpful links to already downloaded items on YotaTech: Not exactly the year or model but points me in the right direction....now all I need is to find this for a 97 lx450

http://personal.utulsa.edu/~nathan-buchanan/93fsm/index.html

http://personal.utulsa.edu/~nathan-buchana.../77exhaustg.pdf

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I know it looks kind of complicated, but as you can see a lot of folks have successfully done it, so it must be fairly intuitive once you get into it.

You'll have to look at it when you get on the yota site, but I'm not sure if anything comes up when you go to '97', because it's the same as '96'. That's the way the EWD manual was. I guess they're trying to save space and not have duplicate files on the site.

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