Toyota Repair: toyota sienna catalytic converters, o2 sensors, dianostics

Question
QUESTION: About 3 months ago, the check engine light came on and after diagnostics, the O2 sensors were replaced. We understood at the time that it might end up being the cat converters. The light just came back on and now the shop (not a dealer) is telling me that all 3 converters need to be replaced to the tune of $2500 for parts and labor. The van is a 2002 with about 175k miles. Is it common for all 3 converters to need replacing? If we do this, can we expect to still drive the van for another 50-75k miles? I don't want to get a new car but don't want to sink money into a car with a short life span. Your input is greatly appreciated!

ANSWER: Hi, Amy
What I would recommend is to get another opinion pfererable from a Toyota dealer, by the way do you have the diagnostic code numbers available? I doubt that all three converters go bad, it sounds like the repair shop just wants to replace all just to cover themselves. The two front converters do go bad, this is not uncommon but is usually either bank one or bank two so if you can reply with the specific code numbers I can look into this a little deeper

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QUESTION: Thanks for the reply! Unfortunately, I was not provided with the diagnostic codes. They did explain why they said all converters need to be replaced. They said their understanding is that if the back one is bad, then all others in front of the bad one need to be replaced too. I did consult with the local Toyota dealership and they seemed to believe it could just be a single replacement. I will take it in to them to verify the diagnosis.

Answer
That's a good idea, spending about $90 to have the tests and dianostics done may save you a lot of money, the reasoning of that repair shop doesn't seem right,neither does their unwillingness to offer an explanation, there is a way to test each converter using the diagnostic equipment the dealer has and they should offer you a printout of converter performance and explain why they would need to be replaced