2004 Toyota Sienna - check engine light

The check engine light on my 2004 Toyota Sienna is on. Vehicle has about 140000 miles. A check by AutoZone found that the code was P0430 = Bank 2Cat Conv. What things could cause this code - bad cat conv, bad O2 sensor or something else?

Bad cat converter or bad O2 sensor.
10 years and 140K is right in the “normal” lifespan of Toyota converters. Save your pennies and find a reputable independent repair shop. You’ll save hundreds over a dealer.

On the sienna with the mileage you have I would almost guarantee the cat is belly up.
Find a shop with a scan tool and have them check the performance of the O2 sensors and go from there.

If you google “Toyota P0430” or something similar, you should get some info on what things could cause this code to appear. Experienced Toyota mechanics would have a checklist of tests to do to decide what was actually wrong. If that’s the only code though, no codes for engine misses in particular, I concur w/TSM above, it is likely simply that you need a replacement cat. Before replacing the cat though, make sure all the routine maintenance suggested in the owner’s manual is up to date. You don’t want some other problem to cause a rich mixture and foul up the new cat too.

I agree there’s a reasonable chance the cat is gone, but as others have noted, it’s definitely worth having the O2 sensor checked first.