I know this one has been covered before. I searched and read previous posts on this including how to test both the EGR valve and modulator. I'll do that when I get home tonight. My question though is this:

After getting cel code 71, I cleaned the EGR sensor and the modulator (filter element had lots of carbon junk) and the error code hasn't come back... yet?

I took the truck to get smogged and it failed the 25mph test, too high on Noxx. Anyways, I noticed that it idles at 1000rpm in gear, and 1200rpm when in park. I know both are high, which makes me suspect it's the EGR valve, however what accounts for the difference idle speeds?

What should be the order of replacing parts? The smog guy said check timing first, then EGR valve, then catalytic converter.

did you check this thread? CODE 71 thread

i was told at a check only that high NOx is from that little black round deal... the egr recirculator.. the plunger in it rips and it stops working.. 50 bux from the dealer.. minus a discount.

a little cheaper than a cat.. good luck..

i'm having the same problem.. i had to reset my light before i took it to the smog station.. luckily it didn't come on while i was there

What I did was I picked up a used EGR valve and switched the reciculator thing out with the one from my 22RE. They have different part #'s, but look the same. The truck has ran about 200 miles since then and the CEL CODE hasn't come back. I took it back in to get smogged but the timing was off (I backed it down too much) and the guy wouldn't let it pass <img src="/forums/images/graemlins/bird.gif" alt="" /> Apparently it has to be within 3 degrees from stock and I had it 5 degrees off so I know these smog guys are just being A-holes.