Originally Posted by F2CMaDMaXX

I can't say this for 100% certain, what i can tell you is the following:

AF ratio on the 2004.5 and onward, cars, is read by factory wide-bands sensors, instead of the regular O2 sensors that most factory cars use, especially up to that point in time.


Even with the older/simpler O2 sensors, the front or, upstream sensors are the ones responsible for reading AF ratios, they read a certain AF and the figures were used by the ECU to add/remove fuel. The rear were only used to detect a certain range, if the readings were in a certain range, then the cats were deemed ok, if not, they just enabled a dash light, nothing more.


On the 350z, the service manual states that which i just mentioned above, with the exception that, 'under certain conditions, the rear (downstream) sensors are used to calculate AF settings'.

It seems that these 'certain conditions' are during Stoich, cruise conditions with light throttle. What seems to happen, is that instead of just reading the rear sensors and saying yay or nay for the cats, it actually takes the readings and applies them to the fuelling data!


So, turning off the warnings in a tune, means that with hiflow or no cats, the ecu sees a cat problem, but doesn't flag the light on the dash.
The problem comes that the ECU still has the option to take the AF data and make adjustments from it, i believe to the long term trims.



So, disconnecting the rear sensors will do two things; Cause the ECU to not read info about the cat condition, it'll therefore flag a cat problem. Secondly, it will obviously not be able to read fuel conditions, in short, it will actually flag a sensor problem, rather than anything to do with the conditions they're reading.


I do not know how this will affect any long term trimming of the fuel tables, i don't believe it will, but who knows.

So if you're sometimes having a problem going from a cruising condition to accelerating, you're coming off perhaps badly set long term trims (it gets set rich), back onto the 'live' readings from the wide-bands, yes, you could have this problem.

I will be able to disconnect them in the next few weeks.

Originally Posted by F2CMaDMaXX

So the lose ends will be at the harness bracket, not at the sensor/exhaust end, i wuold stick some tape around the ends and zip tie them facing upwards, they'll be fine unless there is a torrential downpour.