03 JCW, 15% pulley, MSD ignition, JCW intake and exhaust, and no other real engine performance mods, threw a 2096 "POST CAT FUEL TRIM TOO LEAN BANK 1" code. I noticed the next day that there was an exhaust leak, wound up being a crack in the cat. Had the cat replaced at an exhaust shop, code went away within a day of driving, was fine for a couple weeks, and now is back, same code.

Car seems to run just fine, and ran fine before and after the code first showed and disappeared. Is it likely that one of my O2 sensors was hooped by the computer richening up the mix during the 3 or 4 days I drove it before I could drop it off at the shop for the new cat?

My only other thought is maybe these weird E3 spark plugs I bought to tide me over during a major service about 6 months ago, while I waited for the NGK's to come in. I have yet to replace the E3's because I had no problems, but I've heard that they can cause some issues and throw CEL's for some reason, and am wondering that maybe one is fouled a bit, but I think that'd cause a too rich code. Either way I am just going to put in the NGK's.

Anybody have any ideas? I'd really like to avoid having to replace my O2 sensors, but I didn't replace them during the major front end service and the car is probably still on the original set at 130k miles.

 

My guess is there is a hairline crack in a weld. They don't usually crack at the CAT. they usually crack at the confluence or the first CAT. It can be a hairline crack. one you cant really see. This is what happened to me twice. I replaced the complete header with a used unit. if you don't clear adaptions. the pending code will clear itself and light will turn off within 6 complete driving cycles. If there is no leak detected. Then after 40 complete driving cycles the computer will delete the stored code.


I will be sealing up mine and pressurizing to 10 psi and putting in a water tank. sometimes these cracks are so small you cant find them with smoke. yet the O2 sensor is so sensitive it can see the extra oxygen molecules and pop the code. this is why this code is such a bugger.

 

Mine definitely had a hole in the cat - it had an audible leak and visible hole on the cat - i did ask my exhaust guy if he saw any leaks or cracks in the manifold too, he said no, but was probably more focused on the blatant, obvious leak.

does nobody else have any ideas before i take it in, or is everyone pretty much in agreement that there is likely a crack in the manifold? Does that code point to a crack being before or after the front o2 sensor?

 

2096 Code can't be cleared just by clearing faults. You need to use a real diagnostic tool to clear the memory also. If you don't the fault will just pop back up.

 

So what about it going away for a week or so and then reappearing? Should i have the code reset first? Will a regular obd2 code tool be able to reset it or is that a dealer only MO?