Apprentice here, sorry if this is basic. Replaced an inductive prox on a cylinder end stop yesterday. The one in stores was a 2 wire type. The old one was 3 wire I think, it went in the bin before I looked properly.

PLC is a 1214C DC/DC/DC, sensor goes to I0.3 on board. Input stays on with nothing in front of the sensor. Measured across the input terminal and M with the target away: 6V. With the target in front, 22V.

Tried: moved the sensor to I0.4, same. Second 2 wire sensor from stores, same. So it isn't the channel and it isn't the sensor.

Is the input board damaged? The spec says an input needs 15V to be on, and it's on at 6.