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Does anyone know if the pins on the two-pin Bosch knock sensors are polarity sensitive?
They have no polarity as such.
Actually, some are. To confirm you have to check resistance between the centre boss and both pins. If either pin has continuity to the centre boss then that must be connected to the ground pin. This video shows a nissan sensor but certain bosch part numbers are the same: https://www.youtube.com/watch?v=ZSZSDDRe6Js&t=2s
Of course Adam is right. I had previously seen that video as well. Interesting how the video creator mentions that the sensor that is grounded to the engine will be noisier than the non grounded/polarised type.
Thanks for your help! I do have the Bosch sensors (part number is on there, just like on the video).
I have the same question at the moment. My Bosch knock senor has no connectivity to the center boss from neither of the two pins, but if I measure ohms its not the same resistance from pin1 to pin2 than from pin2 to pin1. One is about 5.3MOhm and the other way around its 4.5 MOhm. I tried many times, its repeatable. So at least electrically its not the same. In the official datasheet Bosch says pin1 is sensor+ and pin2 is sensor-. But there is no clue which pin is 1 and 2. No drawing or anything.
I am still confused and not sure that there is no polarity with these to be honest.
I would probably try measuring voltage between 2 pins with a multimeter while tapping the sensor slightly. If signal voltage is positive, you guessed polarity correctly. Vise versa, negative voltage reading would indicate wrong polarity.
Unfortunately, I can't test it myself and I don't have enough experience in electrical diagnostics, so it's just a theory.
Adam has identified the only case where you need to be concerned with polarity. Otherwise it doesn't matter. The voltage differential will go both positive and negative depending on the noise level, which phase you are in is not important, only the amplitude.
Thank you for pointing out my error.