i know there is a tsb on this. my brother has a 01 2500hd with 8.1 and he put the sealer around the air box but did not fix the problem. the next step is to replace the flap motor. i want to know if this will fix this because you have to take the dash apart to get to the motor. my truck is a early 02 with a d/a. also would like to know if the air box needs the upgrade. thanks for all your help.

I have the same problem. Would be interested in the solution.

Thanks

I had the same problem with my 99 and my 02 HD. They fixed the problem under the hood. Later! Frank

I got this reply on the chevytrucks forum on Yahoo. Its been to cold for me to try it yet (truck wont fit in garage).

"I think theres a bulletin on this, You need to remove the black plasitic cowl by the wipers. on the right hand side you will see a small rectangular cover on the top of the firewall that looks like it has been painted over. cut around it with a razor blade and remove it. below the cover there should be a rectangular duct with a gap (maybe 1/2 in wide)between it and another duct piece. The gap will be about 1 1/2 in below the rectangular cover you removed youll need to seal up this gap, butyl tape or silicone work good. then reseal the cover with silicone and let dry, that should take care of the air leak"