Hi,

After 500+ km (~1000 miles) of my custom exhaust usage I received codes on too lean fuel trims post cats (Post Catalyst Fuel Trim System Too Lean Bank 1 and Bank 2).

O2 sensors are in emulators (not straight bolt into a cat, but a 90 degrees bend). Cats are 200 cells magnaflows.

Car has a tuned soft - not yet adjusted post an exhaust swap.

As it was working well for quite a long distance, thought it will be fine for ages. But unfortunately it is not.

Workshop manual suggest air leaks between o2 sensors (before a cat) - not too possible; Or dead o2 sensor - which would be weird to get both dead at the same time (both bank 1 and bank 2 errors showed up at the same time).

AFRs are good - rather too rich (below 14.7 all the time).

I will try with replacing both o2 sensors. But happy to hear your suggestions on these two specific codes (p2096 and p2098). Maybe someone with 200 cells catalytic converters had similar problems...

Thanks!

 

Error in a title - should be p2096 and p2098 - it is about too lean fuel trim.

 

O2 sensors are in emulators (not straight bolt into a cat, but a 90 degrees bend).

The answer is right there.

 

Well, sounds super logic (that was also my first thought). So should I go straight to a cat with an o2 sensor, given 200 cell cats? Won't it cause too rich fuel trim error?

 

Put the O2 sensors in the exhaust stream properly, the downstream sensors are used for fuel trims.

You will only get faults P0420/P0430 for catalyst efficiency, which any half-decent tuner can disable.

That's about all there is to it.