04 TL 6MT, 240K miles. Check engine code was 0420, indicating a bad cat. This car actually has THREE catalytic converters. 400 bucks for the part and 4 hours of labor to replace it later, 1000 bucks. What is a reasonable time/miles for a cat? I can only assume it uses up all the material in it after so many miles and exhaust. If one went bad I can only assume the other one is on it's way out.