Diagnostic code produces P0420 catalyst system efficiency below threshold-Bank 1. Probable causes are listed as follows:
1-air leak in exhaust before rear H02S
2-AF sensor error
3-Fuel system fault
4-faulty catalytic converter
I've read posts about people replacing all of the above and the problems still exists. I have also read that there is a Toyota service bulletin in regards to this problem with my particular car. There is supposedly some sort of computer glitch which requires it to be updated. My car is over 80,000 miles and older than 8 years. I bought it used, it still falls under the used car places warranty, but i believe the toyota dealership is the only place to get the computer glitch fixed. If it has to be bought to the dealer to get fixed who is responsible for the bill? Also which of the possible causes do you think is responsible for the check engine light?