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Q: Catalytic COnverter and O2 Sensors on 2005 Hyundai Tucson

My check engine light is on, I had a local muffler place diagnose it, (they said codes "B251 and B252") and they said I need 1 new cat converter and all 4 of my O2 sensors replaced. To the tune of $1499 + tax. Does this sound reasonable? They said my one cat converter went bad because of bad O2 sensors, that O2 sensors need to be replaced every 100,000 miles. I am thinking of getting a second and third opinions....
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This sounds ridiculous. I do Emissions work in California and I deal with this stuff every day. First and foremost what is the exact code or codes? Then I can help you. The oxygen sensors don't cause the CAT to fail, it is usually a misfiring engine that wears out the CAT. Some cars just have CATs that wear out sooner than others. Let me know what the codes are and I will help you .
They just told me that the codes were "B251 and B252" -- which mean replace the O2 sensors. I was having another repair place price out the same repair work, but sounds like I should have a second opinion diagnosis as well!?

Sunday Oct 10, Ok so I went to a local shop and had them diagnose as well, and they said my check engine light is coming on because my manifold cat converter in the front is not running efficiently. Said I could wait on getting it repaired until after market parts come out, as right now is a dealer only part and very pricey, and is not broken just is not running efficiently. They said all my O2 sensors look good! Also said that the rear cat converter isn't even hooked up to the computer codes, so the check engine light would never come on when the rear cat converter goes bad! Sounds like the guys at Meineke just wanted my $$$$. I am curious now, I may take to the dealer next weekend see what they have to say!

OCTOBER 16, 2010
Took the car to a local dealer (ugh, relucatantly!) but I wanted to see what they would diagnose. After 1 hour, came up with computer codes of: P0430/ P0420/ P0301/ P0303/ P0305/ P0300. They wanted $275 to "further diagnose" and take apart my engine to actually tell me what needed to be fixed. Isn't that why there are computer codes, so you don;t have to take apart the car to see what is wrong?? I am thinking if I replace all 4 of my O2 sensors and maybe my spark plugs I'll be good??
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