Hallo grumpy 1941, her is grumpy 1956. (that is wat de misses call me, it is not correct she is grumpy)
Yes, if you use a big screw driver between the sensor and your ear as a sound transmitter, you will hear the sensor tikking. Like your doctor checking your longs.
yes (2) your rear bumper must go off for a replacement.
Check the booth, sometimes water in the booth is your problem.
Dutch grumpy from Rotterdam. 🙂