2003 6.0 Engine light on

[SJG 6.0]

My engine light, it doesn't say check engine, it is a symbol of a engine (over by fuel gauge) came on today so I called the dealer to set up a time to bring in the truck and the service guy told me that it is a (emission or fuel issue) He went on to say that these types of problems are hard to diagnose and find on the 6.0 and it probably wont be covered under warranty. He said they would charge me $120.00 to diagnose and "if" it is under warranty I will have my deductible to pay. Do any of you know some things I could check myself?
Thanks for your time

[bigbomar4]

Go to auto zone or advanced auto and see what codes are in it then we can probably help more.

[DozerF350]

I'm not sure if this even applies to diesel vehicles, but I know on gas vehicles, the check engine light will come on if you leave your gas cap off or loose. Have you checked that?

Also, if it's covered under warranty, you should only have to pay a flat deductible of $100 (which I think is BS, by the way). If you're under 100,000 miles, this issue SHOULD be covered (I think).

[SCUFFY828]

I BET ITS A P2285 CODE FOR THE ICP SENSOR , IT DOESNT MATTER WHY THAT LIGHT IS ON ITS UNDER WARRANTY, UNLESS THEY ARENT A MOD FRIENDLY DEALER, AND THE GAS CAP DOESNT EFFECT A DIESEL