On a 1999 e200, two wire knock sensor,

Should there be resistance between the sensors terminals? I get open (no resistance) but I do get voltage when tapping on the sensor.

What is the resistance between the sensor's terminal and its body or ground? should both terminals have resistance to ground? I get none

When the sensor in pluged in, I dont get a code, when I disconned it I do get a code. I tried disconnecting the sensor from the block but ignition timing did not stay advance. I reset the ecu and tried with the sensor still disconnected from the block with sensor being grounded as it should be. still no advance. When I use lower octane gas i still dont get any knock which means the ignition timing is retarded a lot and of course the performance is bad with high fuel consumption.
Wiring from sensor to ecu is ok .

I read that grounding one terminal with a 3300-4500 ohm resistance will keep timing high and ecu will think that KS is connected, did anyone try that and if so which terminal to ecu should be grounded?

Thanks in advance.