Random P0431

[Southtowns27]

'06 LJ, 4.0, 109k miles. I've owned the Jeep for about 5 years and I've always gotten a random P0431. It seemed to trigger most often when the Jeep would be at or near idle for extended periods. I finally got a code for a bad bank 2 downstream O2 sensor so I replaced ALL the O2 sensors with NTK. The O2 sensor code cleared but the random P0431 still occurred. Again, mostly while at low load or idle offroading, sitting in traffic etc. I added the spark plug anti-foulers to the downstream sensors just as an experiment with no change. The code pops up then clears again in a couple days. Then it can be 2 days or 2 months before it comes back. It doesn't cause any drivability issues, it's just kind of annoying. Any ideas on where I go from here?

 

[P man]

Just as an adder P0431 is a 2nd bank warm up code so have you inspected the downstream cat? I wonder if it could be a pcm related issue @Wranglerfix ??

 

[Wranglerfix]

The 0431 code usually leads back to exhaust or intake leaks.

https://www.engine-codes.com/p0431_jeep.html
@Southtowns27 Have you had the exhaust checked for leaks/smoked?

Thanks,

Mark

 

[Southtowns27]

No I haven't had it checked for leaks, but I don't hear anything. How sensitive is it?

 

[JKP]

The precat bolts loosen up at the manifolds. Then you get the efficiency codes.

Looking up from under the Jeep check the 4 precat to manifold bolts. You'll need a fairly long extension on a 3/8 in ratchet and a 15mm socket.

 

[Southtowns27]

Ok cool, seems easy enough. I don't hear a leak, but maybe it's just small enough to be causing my issue.

 

[JKP]

I don't ever hear it. But when the codes pop up, I can reach under there and wiggle the down pipe and cats. They shouldn't move.