hi everyone i'm a P-plater and I currently have very little knowledge on these vehicles, but my bf falcon's check engine light has come on, the oil is fine, temperature gauge and coolant level is fine but there is a rattle in the exhaust and a possible leak somewhere along the top end of it. could anyone tell if that would be causing the check engine light to appear. thanks only new to this so if you're only going to be negative please don't bother.

Collapsed cat converter. causing the rear O2 to throw the CEL.