help with code p0401

Howdy,
My tacoma recently showed code p0401 egr recirculation issue.
98 2.4l with 138k miles. Truck only traveled 2k in the past year. Weekend truck.
The 2 O2 sensors are less than a year old.
Took egr valve out and it was dark but no real build-up. It opens with vacuum and closes fine too. With engine on a little vaccum opens the valve and engine almost turns off.
Took pcv valve out and it looks clean. Put my mouth on it and it seals one way and opens the other.
Took what looks like a temp sensor by egr from manifold it had considerable build-up that I scraped off and left it with a shiny copper surface.
Took egr vacuum valve out but no idea on how to test this, it flows air from all ports. Like all ports are open to atmosphere.
With engine warm and rpm over 3k there's no vacuum at egr.

Any ideas? How do I trouble shoot these components?
Thanks in advance

 

There are a series of test for checking the vacuum operation of the valve, as well as the signal from the sensor for the EGR. Take a look at these pages from the FSM. They discontinues the EGR in the 2RZ engine after 99, so these may not be exactly matching your setup.

 

Thank you, This helps a lot.

 

Cleaning the egr temp sensor solved my P0401 a few years ago. Did you clear the CEL afterwards?

 

Hi Rick,
Yes I cleared the code and have driven about 50 miles since (70/30 city/hwy) and no CEL yet. I hope cleaning the sensor was also the issue in my case, Only time will tell.

Thanks again