Strange coincidence

[schreip]

I have a strange coincidence that I just can't accept. A couple of months ago, my alternator went out. I had to drive it towards home - went out in a less-than-desirable 'hood - and ran the battery completely dead. When I replaced the alternator, the CEL and TRAC CNTL lights came on. The codes are P0420 and P0430, which indicat cats. I cleaned the MAF and throttle body, change the O2 sensors on teh driver's side, cleared codes, etc. Lights are still on. The dealer wants to replace the cats, of course. I just can't buy the coincidence that the cats went out EXACTLY when the alternator did. Any thoughts?

 

[fourwd1]

First, have you tried clearing the codes since you did the work?
How many miles on the vehicle?