I have a 2005 Jeep Wrangler Sport (80,000 miles) that I bought 2 days ago. Driving home from work tonight I got a 'check engine' light. Took it directly to NAPA who ran the code which came back, "PO431 warm up catalyst efficiency below threshold"
The research I have done indicates a failed Catalytic Converter, or an O2 sensor.
Can anyone explain this code to me a little more in depth and what I can do to fix the problem? I understand the Wrangler has 4 sensors, but how do I determine which one is bad? (assuming that is the problem)
Location: Mount Aukum, CA - El Dorado County about 55 mins from the Rubicon Trail
Take it to a shop/buddy that can drive it and do a real time diagnostic on the above mention associated circuits (takes high $$$ toys). They will be able to isolate the offending parts. Other than that, it is a trial and error assault on your wallet.
Technical Description: Warm Up Catalyst Efficiency Below Threshold (Bank 2)
What does that mean?
Basically this means that the oxygen sensor downstream of the catalytic converter on bank 2 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
You will likely not notice any drivability problems, although there may be symptoms such as a rough/hard idle when cold.
A code P0431 may mean that one or more of the following has happened:
The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak
Inspect for exhaust leaks. Next step is to measure the voltage at the oxygen sensor on Bank 2. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
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Bad intake manifold gasket cured mine for awhile she came back I then replaced
My 02's and have been good ( no CEL ) going on three weeks "knock on wood" the cat would probably be next although seems alot of mechanics were dead set on replacing mine from the start. My jeep would whistle really load till wormed up caused by the bad gasket letting the gas station dude know I was there and have my coffee hot and ready.
One of the listed causes is exhaust system leak... Found 2 holes in the muffler from where the rear driveshaft hit when it broke and spun... Hoping this was the cause of my P0431. Just JB Weld-ed the holes. We shall see. (2005 Wrangler X)
When I had the same code on my 05 TJ, one of the mini cats had a hole burned clean through it. It was still under the 8year/80,000mi federal emissions warranty though, so nothing out of pocket for me. Hope all works out for you.