Need help with codes being set

[cowboywildbill]

This isn't a diesel question but, a friend of mine has a 2001 Yukon with 89,000 miles on it and it keeps setting the codes P1404 and P0446.
Apparently the dealer keeps clearing them and say's it's not a problem and all is OK, but can't or won't tell him what the codes are for.
If someone knows the specific problem of each code and a possible cause we would really appreciate it. Thanks

[Kennedy]

Going by my listing, P0446 is Evaporative emission vent system, and P1404 is EGR closed performance.

I haven't messed with a gasser in quite a while, but the P0446 could be related to fueling, removing fuel cap with the engine running, or just a defective cap. The P1404 could be a dirty EGR valve.

One of our GM Techs could likely verify/refute/expand on this.

The 1404 interests me as I've seen this on Dmax trucks with altered EGR systems.

[White Truck]

To add to JK

[cowboywildbill]

Thanks so much everyone for the reply's. I will let him know what the codes mean. It sounds like he needs to try another dealer because if I understand it correctly the emmision's part of the vehicle are under warranty for 100,000 miles for some things. Thanks again.

[GMC Tech]

P0446 relates to a vacuum decay rate being too fast. This could be caused by a small leak in the evap system. GM dealer should have a smoke machine to test the integrity of the evap system. Most of them I find to be the o-ring seal on the top of the fuel tank. Has it had a fuel pump replaced lately? Also GM has a service bulletin related to this code that may apply.
Bulletin #04-06-04-055
P1404 related to the closed position of the EGR valve. valve position sensor voltage less then the minimum learned value. May be a PCM software update for this.
As far as the emmision warrenty, only the Cat convertor and the pcm are covered for 8 years or 80,000 miles. All other parts are 3\36.

[madmatt]

I've gotten numerous other sensors and seals replaced well after the 3/36 under the FEW. The FEW basically states that anything that can cause you to fail a VET, can be covered under warrenty. In the closest area to me that does VET test and maybe this is everywhere, but there if you have a SES light on you fail.