You should post on the electrical wiring forum - a bunch of licensed electricians hang out there.

If you de-power the range by turning off its circuit breaker, then test, the sensor should show no voltage present. Then pull all of the top heating coils and re-power the range. If the sensor indicates that there is no longer a voltage present, then it would seem that a coil has an insulation breakdown inside. You can replace all coils if they are all old, or re-install them one at a time, making runs to the breaker before and after, to find the bad one. Always check with the sensor before handling the range to avoid the consequences of mistakes in breaker use.

If the voltage remains with the coils removed and the stove powered, then there is likely a breakdown somewhere within the stove and a professional repair is called for. This could lead to a call for an electrician. Older stoves used neutral for a ground path, and if the neutral to ground bond in the breaker box is not good, the stove shell voltage can float above ground.

What concerns me most about this is that the shell should still have been more or less grounded and the voltage present too low to light the sensor. A coil insulation breakdown should trigger the breaker to OFF or blow away the internal short. So after the cause of leakage is fixed, a means of grounding the stove should be addressed.

kas