Originally Posted By: zrxkawboy
2005 T&C 3.8. 129k miles. Several months ago, I got a P0420, Cat Conv efficiency below threshold. Over the past couple of months, it has gradually lost power, to the place that it now falls on its face if you give it WOT (won't rev past about 4k). Between the code, the loss of power, and the fact that it's an oil burner, I'm thinking the cat is plugged. Sound like a reasonable diagnosis?
I think you're on the right track. I'm helping a friend with an 08 Expedition with a P0420 code. We cleared it, a day later it came back with a cam position sensor, bank 2, and no P0420. We swapped that out cleared the codes again, and P0420 came back. He wants to change the plugs and coil packs since the truck has 102K miles on it. I told him that was a good idea but it isn't going to solve the P0420 code. He tows a 4,000 lb trailer 5 days a week with it, and it is starting to lose power and ping. The 02 sensors are worth a shot but I think he's looking at a new CC, and so are you. He was driving around with a CEL for a few months now, and I have a feeling he might have had a miss and killed the CC, but I didn't see a code for a miss.