Bad Cats overheat 96 sc400 (168000 mi)?
 

My check engline light is on my 96 sc400 and I get error messages P0420 and P0430 at the same time. I guess that both cats are bad...yet my car has plenty of power and drives smoothly. Will bad cats lead to overheating the engine? I passed my smog, but I am worried about creating damage to my car. Just bought the car yesterday. Does anyone have experience with this problem?

a cat that shows those codes generally just doesn't work as well as it once did...

unless it is coming apart / breaking up internally, you don't have anything to worry about, except the fact that next year it most likely won't pass smog...

one other thing - due to the fact that both codes set at the exact same time, you could potentially have something else going on - wiring, voltage / ground issue, etc... time to start looking in to that, more than anything...

Thank you Creative 84 and Mitsuguy for your responses. The car is driving really well...so I am a little less anxious today. I was worried that carbon build up could overheat the engine by blocking exhaust passage....but it seems that this would be a slow process where the car would give signs of running rough before the cats gave out. I will look into other reasons for the code readings as suggested. Absolutely love driving this SC 400......feels like a new car and it is a 96. Someone also told me that drivers sometimes hollow out cats to get performance....so I will have this checked out too....