Thanks Dave,
Okay, it seems that nobody else have found English versions of the diagrams. I have checked W140 diagrams (diakom.ru), there exists two versions. The one where sensor is connected to pins 22,23,24 of ASR controller and the other version in pins 1,23,34. After comparing the other docs of w124.036 I think that the latter one should be the same as w124.
I have found the sensor under the seat. Since there exists a fault code for the sensor, I'd like to check the wiring and function of the sensor before ordering new one.
Perhaps, I'll need to check German docs.