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E39 M5 O2 sensors
07-11-2019, 06:54 AM
Post: #1
E39 M5 O2 sensors
Hi guys,

The o2 sensors on my M5 have gone. They keep throwing codes. Now to my knowledge the only reason for these o2 sensors is for managing emissions. At partial throttle they help to manage air/fuel ratio in order for the catalic converter to do a proper job. However at full throttle the car throws emission standards out the window and ignores the O2 sensors (again to my knowledge, which in most cases is more dangerous than anything else)

Would it be reasonable to argue that the O2 sensors could actually be ignored completely rather than be replaced? Is it possible to code them out?


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07-11-2019, 07:18 AM
Post: #2
RE: E39 M5 O2 sensors
You can code them out and have the engine run rich.
I would rather replace.

The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end, there it is. ~ Winston Churchill
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07-11-2019, 08:14 AM
Post: #3
E39 M5 O2 sensors
Will a tuner not be able to remap with a dyno? They have probes that measure air/fuel ratio.


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07-11-2019, 05:49 PM
Post: #4
RE: E39 M5 O2 sensors
Cheaper to replace

Call Diesel Electric roughly 1500 each

The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end, there it is. ~ Winston Churchill
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hansie007
09-11-2019, 08:38 PM
Post: #5
RE: E39 M5 O2 sensors
Not recommended, as mentioned the O2 readings gets used to adjust the fuel injection values. Of course some tuners might eliminate the O2 sensors for you but the result is that the O2 map will be replaced by a standard map with no adjustment at all.

If you really want to get technical read up the excellent posts on reverse engineering done on the MMS52/54 DME which will explain exactly how the maps gets used on this engine.

Do you really want to risk destroying this engine for the sake of keeping it in tip top condition and the way it was meant to operate?

This car is not cheap to maintain but in my humble opinion to drive a car like this you should spend the money to enjoy it for many kilometers to come.

2003 E66 760Li
2002 E39M5, sold
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