Sensor on the engine

[sam1806]

Hi I’ve owned for just under a year a 2013 W176 a class I’ve noticed this plug on mine it’s unplugged the picture is just one off the internet iv asked few people and no body knows so I’m wondering if anyone knows what it’s for it causes no problems being unplugged no dash lights nothing and I don’t want to plug it back in Incase the previous owners had it unplugged for a reason
Thanks