I took my wifes Explorer to Advance Auto Parts and they pulled this code. The description reads: Catalyst system efficiency below threshold (Bank 1). The parts guy said it could be plugs, wires, maybe even the ignition coil, I was wondering if just a tune up is in order or is there anything else I should try? It has not returned after a week and we are also having a problem with the 4WD, I put in another post, that may have affected it.

Thanks,
Randy