I have a 96 SOHC 2.0 neon at 102K miles that is throwing code P0401 (insufficient EGR flow). The car runs great but the gas mileage is terrible. I need help finding the cause of this code.
All the vacuum lines appear in great shape though I know I need a vacuum hand pump to know for sure. It is cheaper for me to just replace the small amount of hose involved so I can try that but everything that is vacuum driven works well when the PCM is taken out of the loop (see below).
I have removed the EGR flow tube and inspected it. It is pretty clear - just a light coat of carbon soot. I can blow through it easily. The throttle body also looks the same as does the EGR valve itself (at it's exhaust port). I haven't removed the EGR valve yet.

I temporarily reinstalled the EGR flow tube at the throttle body end and blocked off the other end so that I could run the car normally and continued testing the EGR valve and solenoid.
Standing in front of the car on the driveway, I rev the car from under the hood and I can see the EGR valve move and as well hear the sound of exhaust (and feel it with my hand) coming from the open EGR port (where the tube would have attached) BUT ONLY if I disconnect the solenoid circuit connection to the PCM. I pretty much expect this behavior as I believe the PCM normally energizes the solenoid unless driving fast enough to warrant EGR flow. That's part of my problem - trying to test it while I'm in the driveway. At the solenoid connection, I also confirmed the presence of 12v when the car is running reaffirming the fact the the PCM is shutting down the EGR flow. From what I read the engine must be hot and running above 2000 RPM for the PCM to de-energize the solenoid (thereby permitting exhaust to flow to the intake manifold). I thought I was well above that when reving (and the engine temp show fully warmed up) but I don't seem to be able to trick the PCM to de-energize the solenoid sitting in the driveway. I'm wondering if it ever is.
So at this point I think I have a working EGR valve (it doesn't seem to stick) and moves as expected when the solenoid is de-energized. The solenoid seems to work but I still cannot be sure the PCM ever de-energizes the solenoid.

What else should I check? I hate to put out $80+ for a new EGR/solenoid/transducer just find the the code comes back a week later. I thought about the O2 sensor but I would think other codes would show up if it were mal-functioning.

 

Look, if you don't want to replace the EGR, then take it off and clean the heck out of it and see if that helps. Just hand checking it is not always sufficient. It also helps if you clean the ports on the side of the motor and if you really want to get clean happy, take off the TB and clean it and the intake too. These items get carbon'd up and over time,they get pretty nasty. Soak those items in something like a clean kerosene tank for a long time to make them easier to clean.

You also need to go ahead and do a vacuum check The tool is cheap and the test is quick and easy - unless you just like checking and replacing lines that may in fact be fine.

Now if you just want to get rid of the EGR, buy a block off kit, block off the vacuum lines and the only downside is that you will see the CEL light stay on with EGR error codes forever and ever.

A missing EGR that is properly blocked off is WAY better then a malfunctioning EGR that CAUSES problems. An EGR is NOT required for a car to run, it is just to reduce the NOX and other gasses from your exhaust. Now if you are in city/state that has emissions laws and actively regulates it with inspections, you can't do this.