I wonder if anyone can help me out with either??!! The first is the always popular 0401 code, I replaced the egr valve and the vaccum regulator sensor, still get the code. Everybody says it's the DPFE sensor but when I check the volts on the reference side it's around 5 volts which is supposed to be good. However the signal side stays really low like around .02. Didn't know if that was right or not?? The other is a ticking sound coming from what I THINK is the cat closest to the motor on the driver side. Some people have said cam gears and journals but I was just under it and I swear it's in the cat! Could the cat be clogged up or the stuff inside breaking apart making the ticking and the 0401 code since it does tie in to the EGR system?? Or am I way wrong?? Thanks for the help guys!!!!!!!!

 

Pull the downstream pressure hose off (smaller diameter) the DPFE at the manifold, with KOEO pull about 9 in/Hg of vacuum on the downstream hose and monitor the signal.. Should see a voltage increase better than 4.0 with vacuum applied..

 

most likely its one of the studs in the manifold have broken and leaking. The broken stud alows a little leak between the motor and the manifold wich makes a tickin noise. It is very common on those.

 

It is very common to have a leak near the manifold due to a broken or corroded stud. The same thing happened on my 98 expedition, one of the studs broke and it was leaking pretty noticeably. The repair cost on those is usually pretty high but i found this relatively inexpensive part that worked wonders for me, it fixed the leak and only took a matter of minutes to install. check it out:

http://the-hush.com/

i ordered it online and it worked for me. hopefully it fixes your problem.
-good luck