Empty fuse slot, what does this "AIR" fuse do??
 

Hey guys, I was going through all the fuses in my 2002 sierra's fusebox to replace the ones that were burnt and make sure all the rest had the proper fuses considering I bought the truck about 7 months ago.

In the fusebox under the hood, there are multiple Large fuses at the top. One of the slots is empty. It has metal fittings installed, so it seems as if a fuse is suppose to be there. When I check the cover, it indicates "30 amp AIR" I searched everywhere to try and figure out what the hell the AIR slot meant, but haven't seen a clue. Everything Air related in the cabin SEEMS to work, inlcuding heat/A.C, blowers, etc.

Anyone have a clue? Thanks.

Think thats for EGR equipped and AIR pumps.

EGR equipped? Um...Ok, correct me if I'm wrong, but aren't EGR systems included in all vehicles these days? I mean considering it reduces harmful emissions, increases fuel mileage and horsepower. And being equipped with one and the fuse missing, wouldn't that cause a whole new set of fuel supply/air intake problems?

I don't know what models do and don't but many late model Silverado's, mine included, do not have a EGR valve and pump. Obviously they've learned to pass emissions without them. Tuning is my guess. Look on your exhaust manifolds, I'm betting it doesn't have one.

Up to 02 you should have EGR, I believe that's when they phased it out. Some 02's have it some don't I believe...my 02 PCM is for a non-EGR equipped truck. Some earlier models also had air injection, which included an electric air pump which pumped air into the exhaust to help oxygentate the cat converters more quickly. The non-AIR equipped trucks will still have the slot for the fuse in the fuse box. My truck was originally equipped with EGR and no AIR. It's my understanding that very few of the trucks came with AIR actually.

I would guess this fuse slot is only used for trucks with an on board air compressor for the models that came with load leveling shocks.

You're right, it was for cold engine startup conditions where the Catalysts needed additional oxygen for 2 minutes in order to light off quickly to reduce cold start emissions. I believe it was most prevalent in California trucks, I know my 2001 has it. The later years 2002-on have closer coupled catalysts which heat up quicker in turn reducing cold start emissions, negating the need for the additional AIR equipment; they are another big reason why longtube headers are essentially illegal, the cats are too close to the manifolds to get a long enough primary to be worth while. :barf:

From the service manual. AIR Fuse #4 - Secondary Air injection reaction pump

Ok, excellent, thanks for the input peeps. Well, you're right, I don't have EGR which I believed all newer vehicles were required to have. I purchased a fuse and put it in while waiting for responses just to see if I'd notice anything different... and no, i didn't. So, regarldess of what it's for, it definitely doesn't seem like something I need.

Well,you have a spare fuse now.