OK working with the dealer on buying this truck. After I told them I would buy it, the check engine light came on. I haven't signed papers, but it is a good deal, so I'm willing to have a little patience, and here's where things are now.

1) Light came on, "Reduced Engine Power" on the display (remember, no fancy DIC in a WT).
2) Dealer replaced EGR Cooler
3) During their test drive light came on again, and they diagnosed to the MAF, which they are planning to replace.
4) Had the VIN run on this site (http://www.dieselplace.com/forum/showthread.php?t=368398) and I noticed that the MAF was replaced about 25,000 miles ago (at 45,000) and the EGR valve replaced about 5000 miles ago (at 64,000).

Truck seems to run fine, I drove it a little this afternoon to get new tires put on it (part of the deal - their $$, my choice). Though I don't have enough experience to know if acceleration is right.

I do not yet know the codes. I don't have a reader. Will probably do that tomorrow.

So, the question that seems obvious is whether all this is actually connected in some way? Is there something else happening causing these failures? I know, the right answer is delete the EGR and Cooler, but dealer can't do that and I still have some warranty if I don't go screwing with things.

Feels like we're dealing with too much soot in the intake side - perhaps the EGR is stuck open? Maybe the DPF isn't functioning properly?

I kinda bothers me that the dealer is just chasing lights and codes. I guess they will eventually get it right, but I don't want to keep waiting...

Thanks!

Check to make sure it's got a stock air filter. MAF codes can be set from over oiled aftermarket air filters, K&N seem to be a good one to cause issues. Just a thought. As far as EGR, not sure, without the codes, hard to say. If not too bad, most MAF codes can be fixed with MAF cleaner spray, CRC makes one. Chris

So CEL is out. Got a reader and the codes below showed up. I didn't get a chance to check the air filter - weather got a little sketchy around here. I'll check the air filter in the am.

Does this help diagnose what's going on?

Code: P0098 Modules: ECM Description: Intake Air Temperature (IAT) Sensor 2 Circuit High Voltage
Code: P0113 Modules: ECM, PCM Description: Intake Air Temperature (IAT) Sensor Circuit High Voltage
Code: P0101 Modules: ECM, PCM Description: Mass Air Flow (MAF) Sensor Performance

Filter is a white paper AC Delco. No oil/dirt in the intake, sensor looking thing (MAF?) looked clean.

Still no CEL.

95% of P0101 codes are due to dirty MAF sensor, from what' been posted here. Most of the time, spray it with MAF sensor cleaner, good to go. The IAT, if I'm not mistaken, is part of the MAF unit. Also, bad connection or wire issues could cause an issue. But the CEL is out, just those stored codes? If you've got the truck, I'd clear the codes, drive it, see if they come back. If it does, post back. Enjoy the truck! Chris

On the way to work this am, CEL came back on. I didn't check codes - took my reader out of the truck since it is supposed to go back to the dealer today. Don't want them to think I'm looking over their shoulder.

I'm going to let them switch out the MAF I need to let them follow their path or they probably won't be interested in other ideas. Who knows, they might be right ;)

I drove the truck a bit this weekend and I really do like it, so, a little patience I guess.