It's been about a month and the same engine light saying "Catalyst Efficiency Below Threshold (Bank 1)" hasreappeared. Can anyone tell me what this means? Actual code is P0420. The last time, I had already cleared the actual code from the reader's memory bank soI couldn't retrieve it for you. My Dak is going back to Dodge for warranty but I would like to know what it's doing...or not doing.

Thanks!
Legacy
2007 Dodge Dakota SLTQC 2wd 3.7 6cyl