First, I would remove the wheels with sensors and take a look at the pad thickness If that side is close to being worn out it is time to replace both anyway. Once you have the pads removed you can see if there is significant difference in wear from side to side. In my experience I can always see some difference. You should replace the rotors whenever you replace pads.

If the pads are not worn out, before replacing a sensor I would unplug the connection to the vehicle, one at a time to see if the dash light comes on. Do not disconnect the sensor at the pads as it is to easy to damage it. Sensors should be replaced when pads are replaced. I buy the sensors sold at dealer, they are not that expensive and I know what I am getting.

That said, I haven't heard anything that indicates your pads need to be replaced. You have no dash light and if they were gone you would be hearing a grinding noise when you brake as it would be metal to metal.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas