Greets.
Well, I'm just back from the dealer. The engine check light came on again (as it has 3 of the last 4 long trips I've made). I've replaced the MAF and O2 sensors in the past. Fortunately, the car was under warranty then. It just came out of warranty so I was dreading this trip.
The diagnosis was P0420: "Catalyst system efficiency below threshold, bank 1."
The test guy knew his stuff though and found a TSB EG024-04. So he flashed the ECU EPROM I guess...work order says, "reprogrammed the engine ECU," and that seemed to do it.
Well, at least the light is still off.
Boy, was that a relief! I expected some kind of, "the frenortinizer is discombobulated and that's a $500 part...oh, and you should have the system purged too--that's $400" thing.
No charge! Thank the gods for the TSBs!
I posted in case anyone else ever has that problem...and cause it's nice to post a positive outcome once in a while....
-Happy Camper