P0401 Death! Was - Check my thinking on New Years Day! (1 Viewer)

[Noahrob]

First of all, Happy New Year! I’ve met a lot of cool people through IH8Mud, hopefully I meet even more in 2020.

Backstory. 1997 LX450 with stupid PO401 which I am happy to ignore, but the smog man has arrived.

One of the things I love about mud is you can pretty much just copy somebody else for almost anything.

The tests I’ve done.
1) EGR:
2) EGR modulator ( which I replaced about 1 year ago): /m.youtube.com/watch?v=WOSFmKY15SU
3) VSV: Checking VSV for EGR easy way P0401


EGR passed, modulator passed, VSV failed ( no resistance and didn’t close with 12v) so I will get a new one and bolt it on the outside of the intake. My question is, am I testing correctly for each component?

 

[Rusty Marlin]

I followed the FSM, and that was a year ago; so going from memory... looked good to me.
There's a hard pipe that passes the EGR vac line through the upper manifold that can get clogged, but based on your tests it looks like its clear.

 

[Noahrob]

Thanks...interestingly enough, I changed out the VSV last year, maybe it was bad? I also cleaned out the port to the TB. I guess I’ll take it all apart tomorrow and recheck.


Slightly unrelated, anybody know if you can smog with an active cel p0401 in California?

 

[Noahrob]

Ok, this is the second time I’ve had the upper intake off specifically for this error code. Turns out that I actually don’t know what fixed it, but here is what I did.

1) I cleaned the living crap out of everything, even if it looked clean. For example, the EGR looked clean, but just to be sure, I went through a half a can of TB cleaner and a toothbrush.

2) several folks say that the TB to EGR port gets clogged and even though mine looked clean, I used the other half of the TB cleaner and a stiff wire as a reamer to clean it out. Some carbon came out, but not much.

3) I thought my VSV was bad, but once I had the intake off, I ran 12v to it and I could hear it clicking. This is when I noticed a bit of air flowing even when the VSV was on. My theory is that that little bit of air was messing up the system and since I just replaced all the hose I decided I would cinch everything up.

In the end, I’m not really sure what fixed it, but the code is gone and my guess is it has something to do with the super powers of neon green zip ties, they just work better