P0420 Code After...

BatMan · Jun 8, 2015

...distributor was replaced.

My 2000 Honda Accord (4 Cyl.) stalled while driving, stalled once more a bit afterwards and completely died on me - the car wanted to turn over while pulled over on the highway, but wouldn't turn on. I had the car towed to a mechanic who told me the distributor had gone bad, so I had him replace it. After I picked up the car I noticed a lack of power/acceleration - at first I didn't think anything of it, maybe not driving my car for 2 days made me forget how the car felt (lol), but then I hoped on the freeway and the CEL came on. I used a code reader (got the P0420 reading), cleared the code, but it came back on.

Thoughts? I've searched P0420 on here and read that it can be the CAT or 02 sensor(s).

Car: 2000 Honda Accord (4 cyl.)
Mileage: 219,000
Problems: CEL on; lack of power/acceleration, especially on the freeway

EDIT: If the CAT is in fact bad (reading you can tell if you bang on the CAT), does anyone have any idea how soon I'd have to replace it?

twofast4u · Jun 8, 2015

So...let me share my experience with this. As the weather got warmer, i started getting the dreaded p0420 code randomly while driving. I already decided to hollow out my CAT if it ever went bad. Few weeks later, i took out my CAT and noticed it was still fairly clean, so i used my air compressor and cleaned out all the carbon from the inside. I put everything back, and I haven't had the code pop up once after that.

I would try that first, then maybe go from there.

xci.ed6 · Jun 8, 2015

yeah, 420 is catalyst

james'99 · Jun 8, 2015

Got an IR thermometer? Check the inlet temp of the cat, and the outlet temp of the cat. Outlet temp should be at least 100 degrees hotter than the inlet.

Due to your issues, you may have a coating of raw fuel on the O2 sensor. My dad would have this issue on his 2002 Tacoma when my sister would stall it on him when she was learning stick and then a week or so of driving later, the code wouldn't come back. Keep clearing it for a little bit, or maybe you want to remove the sensor and hit it with some brake cleaner and clear the code. I'd also check into exhaust leaks pre cat causing a flow of outside air through the catalyst.