The 1/4" phono plug confuses me, but since it's a TRS it has 2 signal and one ground so it might make sense that it could be used for programming whatever's at the other end. So...I'll say alarm. Curious what you find when you trace it.
Or, plug a guitar into it and see what happens. Ohh!!!!! Maybe a Mr Microphone???
I beg to differ. I know it's similar to a head gasket sensor. However, this is a Magneto Reluctance based sensor for the upper reciprocation Dingle Arm. The reason it is hard to recognize is that this is the non OEM version
[google turbo encabulator, for specific reference]