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      06-26-2013, 06:56 AM   #19
Mahmood07
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Drives: E92 M3 + F85 X5M
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Quote:
Originally Posted by Roman@ESS View Post
This could only be from a fault related to a hardware failure or the car was flashed back to stock by the dealer. Read the codes stored and email them to me.
Quote:
Originally Posted by happos2 View Post
Bad pre-cat O2 sensors can affect how your engine runs. This is a great place for the computer to sample the oxygen and determine if the combustion process was carried out correctly (in non-technical terms). Depending on how bad the reading, the car could be overcompensating or undercompensating the amount of fuel input which might cause your car to run lean or rich. It is the post O2 cat that really doesn't matter after you remove cats as it WAS trying to evaluate how effective the cat was.

That being said, I am having the same issue as you. I have a different brand of test pipes and a different stage II tune, however I get an SES light with the faults being the 02 sensors (I made a thread about it in this section of the forum which Alexshop was very helpful helping me decipher what the codes mean).
With that information, I ordered two pre-cat O2 sensors from ebay and will be replacing them tonight or tomorrow.

Hope this helps.
Quote:
Originally Posted by Dave07997S View Post
You can have a post cat sensor go bad even with a tune that doesn't pull codes for inefficient catalyst and kick off a code for another problem. It could be sensing an exhaust leak or the rear 02s can go faulty. I know this happened to me.

Mahmood post the codes and someone will steer you in the right direction.
Quote:
Originally Posted by tim944s View Post
Codes are good. I have had the same. I also had it come sporadically go on and off. Ended up being the fuel pump controller. Same redline and no adverse operation or idle. Just glitchy.
Thanks for the tips guys. I called my SA and he could only give me the codes by phone so here is what I got:

27ca O2 sensor after cat bank 1
27cb O2 sensor after cat bank 2

Does this mean I have to replace the o2 sensors after the primary cats ?
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