I have a SOHC '97 sable. In the Dallas area the vehicle inspection requires an emission test to pass. My check engine light was on all the time and the inspection will not pass with this light on. I had a diagnostic run on this car @ $80.00 and it showed the catalytic convertors to be bad. The diagnostic showed that both convertors were bad, since this car has two, and would not point which one was bad so I replaced both @ $500.00 at a muffler shop. The store that ran the diagnostic quoted me a price of $1600.00. Be sure to get a copy of the diagnostic test when you have it done. It will save you some money by doing this. Hope this helps someone if they have the same problem.

Better solution is to get the repair when light comes on. Simple OBDII readers for around $70. Manual will tell which sensor.Plan on new Upstream sensors at 100k or when smog tests shows deterioration of HC and CO readings. It's about MPG. I use a more sophisticated Car Chip reader for extensive testing.
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wal-mart carries obd2 readers. they can reset the codes and shut the "check engine" light off. it will bring up the codes and say what is wrong. usually the catalytic converters go bad due to a rich fuel mixture or long idling. i would get o2 sensors since the computer of the car does the fuel mixture by the reading the o2 sensor detedts the mixture in the exhaust. if o2 sensors are covered in carbon, they cant detect the fuel as well and the computer causes it to add more fuel to the mix which in turn burns more fuel and can burn up the cat convertors and make lotsa carbon on the spark plugs.

Well shelling out $500.00 is better than $1600.00 any day. $500.00 is actually a good price to remove and replace (+ hardware and labor) two converters. Gotta shop around.

If you don't fix the problem, another cat is guaranteed.
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