[samcrf450]

I have an 04 duramax lb7 motor. I thought there was not supposed to be a cat on it but when I was under the truck yesterday I saw toward the front of the exhaust system a large cylindrical can. Is this a cat? This is an Idaho truck it shouldnt have a cat right?

 

[Mackin]

Why shouldn't it have a Catalytic Converter? In 02 the CA emission trucks and some North East received them.By 03 they were a federal emission requirement (all state) IIR.

That is what you saw

 

[ob_1jr]

Yep, sounds like you have a california emissions truck. (it is up front right after the bend from the turbo?) I have an 04 with the LB7 and I have no Cat on mine. I believe the LLY engine was the first one to have a cat on them for federal emissions.