P402 Won't Stay Away

Having trouble with my 2004 2.7 MT Tacoma

I got a bunch of junk in my air intake and ended up having to replace the Idle Air Control Valve to get my idle to stop surging, but ever since I've had a P402 (excess exhaust in recirculation) that I cannot get rid of. I took it to a garage for some help diagnosing since I don't have the tools or knowledge for that, but have been buying and replacing parts to get a better lay of the land underneath the hood.

They first suggested replacing the EGR Valve. I did and cleared the code after getting the new one on there only to have it pop back up 20 miles later. They said the next most likely candidate was the EGR Temp Sensor, then the VSV. I did the sensor first, code came back again, then did the VSV and it's back again. Getting tired of throwing parts at this and I need to pass emissions so I've got to get rid of the check engine light.

Any ideas before I just find a different garage and open up my wallet? What else can throw a P402?

 

I’d start by testing the VSV for EGR.
Then, possibly the EHR Gas Temp. sensor. (Doubtful this would be it)

 

Is it really necessary to test those two when I just replaced them? They're brand new

 

You replaced the VSV valve?

No, sorry I missed that part.
Dang, you pretty much replaced all the parts.
This could be tricky to figure out.

 

Yeah, so far I've replaced

• EGR Valve
• EGR Temp Sensor
• VSV

That's what I was afraid of. It's already getting expensive replacing a bunch of parts that aren't solving the issue. Thanks for the reply though, and let me know if you have any other ideas!

 

What about the EGR modulator? Get one from a wrecker (to save money) and see if that helps.

 

I googeled ypour issue and I came up with a former member called "vapovic". He had the same problem but his posting is in the 4 cyl section of the forum... I dont think that that section exists anymore. vapovic doesnt appear to be a member anymore as I cant find his name in the search box. Try googling "P0402 Tacoma" and you should see a old (2011) Tacoma world post.

 

Yeah I think that's the next move. I did find this really helpful video where he goes through how to diagnose what's wrong in the EGR system. It looks like EGR modulator is what's left, but it could also be a clogged vacuum hose. I've got a vacuum gauge coming in the mail today to help me figure it out. Thanks for the suggestion!
https://youtu.be/cvo1e4JcfSY

 

I was able to find it and read through. Thanks!

 

Check the vacuum lines for leaks and blockages. Also check the ports on the throttle body where they connect. After I cleaned my throttle body I got this code, and it turned out that most of the ports on it had clogged up with gunk.

 

Didn't find any leaks or blockages, but I did look at the diagram and find that the vacuum hoses were connecting the wrong ports! The ones from the throttle body to the EGR modulator were all crossed. Whenever I took the throttle body off to clean it and replace the IAC valve, I marked them and took a picture to make sure I got them back in the right spot. It's totally possible that I just messed it up when I replaced them, but I'm guessing they got crossed when I took it to this garage to diagnose. So I've spent nearly $300 replacing parts that weren't broken. Oops. Silver lining is at least I learned a lot about the EGR system. I've cleared the code and will be driving it around later to see if it comes back, but I'm hoping that was all that was wrong. Thanks everyone for the help!!