e34 error, rich mixture

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deepblueE34

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Dec 14, 2011
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Hello Gentlemen,

I'm trying figure out why I keep getting an oxygen sensor error. I though maybe someone here might have came across this and has some insights.

The car is e34 520i that has had a M50B25 swapped into it. I'm still using the Siemens DME and all the original sensors.

The problem, in short, is that I keep getting "200 lambda regulating limit" "Mixture limit rich" (please see attached screenshot). And my adaption values are stuck at zero while the lambda sensor voltage is fluctuating within the normal range. Does anyone know why the adaption values are not changing in response to the o2 sensor voltage? I would expect the adaptions to change to trim the fuel in response to the rich condition.

I have change and checked a bunch of things but so far the error persists.

At this point am looking for a test DME so that I can rule out if mine is going bonkers. Does anyone have one for "try" or sale? I can perhaps offer a free diagnosis session in exchange of a test swap :)
 

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Turns out that I have the wrong o2 sensor. The one for the siemens ECU has a different output voltage (0-5v). The one I bought makes up to 1 volts as you can see in the second screen capture. The funny thing is that this o2 sensor has the correct part number but the wrong connector and voltage!
 
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