Lots of great information in this thread. Thanks to everyone who contributed. Several weeks ago I had a CEL P0431 Warm Up Catalyst Efficiency Bank 2 Below Threshold. It came on and off a couple of times over the weeks but the Jeep runs just fine. Very recently the CEL was flashing and the engine running rough for a few seconds after startup then cleared up. Had the CEL read again and they said it was the same code in there three times. I've scanned this thread pretty thoroughly and see that
@Chris says this code usually means a bad CAT. My 2005 with stock exhaust has only 57,000 miles on it. I see other people in this thread with many many more miles before the CATs go bad. Not sure what to do at this point since it would seem odd to have a bad CAT with these miles. Since I had the CEL flashing I dont want to sit on it any more. How many miles were on your CATs when you had to replace them?