# How to check if filament sensor is ok?

The filament sensor of my i3 MK3 stopped working. In the support menu, it just says IR: N/A. This is the same output as if I disconnect the filament sensor.

My PCB says rev 0.2e and this is what I see:

In the Prusa Shop, I found a laser sensor, which has 4 pins, so that's probably what I have.

I have already checked the voltage coming from the Einsy cable. It's 5.02 V, which is probably ok. The remaining two pins seem to be SCL and SDA, so it's likely a I²C bus.

I have Arduinos, ESP8266 and ESP32 around. Is there a test routine that I could run on the filament sensor, other than Prusa's N/A display?