Bad Catalytic Converter '97 Grand Marquis

I have a question for everybody. We have eliminated everything and it is a bad catalytic converter. I just realized that the 97 Mercury GM has two. To keep from purchasing 2 catalytic converters how can I tell which one is bad? Thanks

I have a question for everybody. We have eliminated everything and it is a bad catalytic converter. I just realized that the 97 Mercury GM has two. To keep from purchasing 2 catalytic converters how can I tell which one is bad? Thanks

After reading some more posts and seeing the one about the O2 sensor from Lieutenantcracker I took the car back down to a local shop and got the exact code. This is for everybody who isn't sure, but there are 2 O2 sensors. An upstream and downstream. Make sure you get the specifice code which seems to be 0420 or 0430 and that will tell you which one is bad. Good Luck everybody.

You are correct. P0420 is on bank 1 (passender side on a rear wheel drive V8) P0430 is drivers side. This is another reason to write down the exact code numbers and post them along with your question. Thanks gladmother for your research.