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      04-22-2019, 07:47 PM   #7

Drives: 2009 E90 335xi, 2011 E93 M3
Join Date: Dec 2012
Location: Boston

iTrader: (3)

Originally Posted by Down_Shift View Post
This is because there are two readiness for cats. Not one.
Correct me if I'm wrong;

There is an "oxygen sensor" flag which reports the functionality of the the sensors upstream of the catalytic converter and a "cat efficiency" or "catalyst" monitor which reports on the downstream sensor function.

Upstream sensors are critical to the operation of the engine which relies on them to report A/F ratio.

Downstream sensors are not critical to engine operation and are solely present to verify normal function of the converters

No tune would spoof or otherwise monkey with the operation of the upstream sensors and the "oxygen sensor" flag will always set. The "cat efficiency" flag, on the other hand, is purposefully disabled so that users with test pipes do not have suffer constantly lit CELs. Therefore, the "cat efficiency" flag always reports not ready.

Anyway, I have a VF620 with VF stock tune and test pipes. I have one not-ready flag, "cat efficiency", and I pass inspection.