[1 Lucky Texan]

If your car was recalled and never serviced, it should go in for that (I don't know the nature of the recall, sometimes, they must recall thousands of cars to inspect for a problem that only affects a small percentage)

but generally, the 420 code can be difficult to pin down and while there are some things a home mechanic can inspect for, you may need a professional to help. I will hazard to guess that, if your car has been running well and getting decent gas mileage, i doubt the cat conv has been significantly damaged.

 

[1 Lucky Texan]

I was re-reading and thought I'd ask - have you had the timing belt changed? If not, you're overdue.