Insufficient EGR flow P0401

Hey fellas
I'm struggling to get my 98 tacoma 2.7l to pass smog here in California. Emissions are good, but I have a pesky P0401 code that won't leave. I did some brief research and pulled my EGR valve and the modulator. I checked the modulator diaphragm and it is in working condition, and the EGR valve doesnt have any gunk build up (I still sprayed it with carb cleaner because why not). I dont have a vacuum pump to test the egr valve, anybody know any alternatives? Also is there anyone else that has successfully removed this code using different methods? I have 20 days left on my temp registration to get it fixed.
Thanks

 

i did this 2 smogs ago(CA also, sux). cleaned the shite out of the whole egr system and still had the code. changed out the egr valve(bought from dealer for too much but try and find a partout) and code was gone and 2.7 passed.

 

You don't really need a vacuum pump to test the EGR valve, just disconnect the vacuum line (opposite end of the line from the valve itself) and just suck on it. If you do it right, while idling, and the valve is good, it should stall the engine or at least make it run real rough.

Its easy to blame the valve when the EGR system isn't working right, but its likely the most reliable component of the four. My P0401 was caused by a gunked up EGR temp sensor. Removed it, cleaned it up, and re-installed. Problem solved.

 

I had the same code and replaced the EGR sensor under the intake manifold. (The Green plastic one that's hard to get to) code went away.

 

Thanks for the advice
@Tan4x4 I tried sucking in on each of these vacuum lines (marked by the red circle), and nothing happened to the idle. Are there any other tests I could do?

@saggio I found the green plastic component, it appears to be the vacuum switching valve not the temp sensor. I hear the VSV can also lead to the P0401 code, anybody know any methods to test it?

Also where is the EGR temp sensor located? I didnt immediately see it anywhere.

Thanks for the help guys I really appreciate it. I don't have any mechanical background but I'm trying to learn as I go

sincerely,
Wishing I didn't sell my smog-exempt diesel

 

I'm gonna guess VSV.

Dried,cracked and swollen vacuum lines don't help, either. I'd replace those.

 

I agree. THat's an easy fix, too.

 

The way I test the EGR valve (the shiny thingy in your photo), is to wait until the engine is cool, and reach down and locate where the vacuum line connects to the valve.Diisconnect it temporarily, and connect a 2-foot long piece of extra hose (with the same inside diameter) to that nipple. Then run the test. If that does not affect the idle, then your EGR is stuck closed.

The temp sensor is barely visible in your photo. Its hidden under that larger-diameter hose (going left to right). You need a sensor socket to get it off, or a brake-line wrench (like a box-end wrench with a gap). I don't remember the size, either 12mm or 14mm wrench.