I am not sure because of BMW's sensitive nature on O2 sensors. Cat does not degrade unless something caused it to fail in the first place. I will look into it, but it is very tight space under there due to AWD.

I am going to try straight gas and see if anything changes on X5.

is straight gas supposed to be running much more cleaner without any ethanol content?)

Monitor your real-time voltage at post cat and pre cat. The post car should not track up and down with pre cat. If they do that means the cat is worn out.


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“Straight” gas?!?! Like not gay? Not unleaded?!?

Or just ‘unleaded gas without ethanol’? ;)

Wont matter, IMO

N52 29F4 and 29F5 codes
 

Pure gas won't make a difference unfortunately.

Oh well, I am just going to order the O2 sensor extender and hope itll turn off the check engine light.

Update: I ordered 2 o2 spacers with mini catylst from Aliexpress and the check engine light went out on its own. I finally passed emission.

I have had nearly 100% success with this method.


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