I've been driving with CEL turned on for around 30.000 miles. The performance never changed, so I didn't pay much attention because of CEL.
Yesterday I finally connected code reader and got P0401 error. I've searched the forum and it's probably bad EGR valve or DPFE sensor that's causing the error (maybe EGR valve is dirty... it wouldn't be surprise as it's quite common problem here in Europe, because of low quality fuel).
All in all the car, which is all stock, is running normally, it starts OK (maybe not so smooth when it's cold, but this is probably caused by at least 5 years old battery and not EGR valve), it runs smooth, it is responsive and I guess 23 mpg is normal fuel economy. The only problem I have with this car is AT (not completely smooth gear changing and harsh reverse... but this is probably caused by something else and not EGR vlave... I'll try to describe it in another thread).

In this way I have no intention of replacing EGR valve (I will probably only try to clean it), but I would still appreciate it, if someone maybe have some experience with P0401 error causing some other major problems.

Thanks in advanace!

 

It's common for the plastic egr housing to crack and leak vacuum, or one of the hose connection fittings to crack/break, both will causing the error.

 

Plastic housing and connections seems fine. I removed EGR valve today and it doesn't look dirty at all. Maybe the tube that links EGR valve and exhaust manifold is dirty, but it so difficult to unscrew it... I just couldn't reach it with wrench as there is so little space around exhaust manifold. Any ideas how to unscrew it?

Position of vavle is closed (I mean the valve is blocking the exhaust gas intake) which is probably the right position with engine not running (I've read that valve is opened only at steady speed (driving on highway for example). But maybe the valve is stucked and it doesn't open when it should.

What about deleting the EGR valve? Has anyone done it on S197 model? It shouldn't be difficult, but I don't know how to close vacuum line?!?

All in all... here are some pics of EGR valve:

 

The issue is that the MAP sensor is integrated into the EGR system as well.

You can have a tune disable egr, and as long as the valve is closed, it'll be ok.

(removing the feed pipe at the bottom end shouldn't make a difference; there is nothing to clog).

Most likely the egr unit itself is defective, or the sensor built into it is bad.

 

I cleaned the EGR valve anyway and installed it back... but as expected, CEL turned on after few miles. It really seems that EGR unit is defective and should be changed, but I won't do it... if it didn't effect the performance for last 30.000 miles, then I guess it won't effect it ever.

What if I delete the error code with Torque application for android (with OBD bluetooth scanner)? Will CEL turn on again after few miles or will it be deleted permanently?

 

I connected Torque app to OBDII connector while driving to work today (I still didn't delete the CEL).
I got this I/M readiness screen, which I can't completely understand:



How it says EGR sys: Complete, while I get P0401 EGR trouble code?!?

 

That's fantastic for checking inspection readiness.

The egr looks good; must just have a bad sensor in it or something.

 

So if I understand correctly... EGR is still functional, only sensor reading is wrong, right?

Yes, Torque app is great. It enables you to inspect so many parameters that you simply must have it.
It also measures acceleration from 0-60 mph and horse power. I plan to do some mods (CAI, true dual exhaust...) in following month, so I'll see if there will actually be some performance improvements or is it just a myth.

 

If the car has a DPFE sensor (Delta Pressure Feedback Exhaust sensor), that's most likely the cause for that P0401 code. We replaced a ton of DPFE sensors on Tauruses, Rangers, Explorers, and many other vehicles for EGR codes, early/mid 2000-model cars

 

I guess the car has DPFE sensor, but it if I'm not mistaken, sensor is integrated into EGR module... in this way you can't replace it separately (you must replace the whole EGR module).