Toyota Repair: 2002 Toyota Sienna Emissions Problems, catalytic converters, siennas

Question
My son has a 2002 Sienna with the check engine light showing consistently.  The car has 100K miles.  The dealer says the catalytic converters are shot and the EC computer is going bad.  They want $4000 to fix the car.  Is this a common problem?  Any insight and advice will be appreciated.

Answer
I would really need to know the diagnostic trouble codes, did the dealer give you those, if not they should. Yes there have been and are some problems with the catalityc converters at this mileage but replacement of the ECM doesn't sound right to me, not a common problem on the siennas, this is why I need to know the code numbers,just the numbers, nothing else. If you can do that then I can have a much more specific answer for you.