Check gauges light

My wife told me the check gauges light came on last week the check engine light flickers ipulled a code which said running lean but no mention of anything else.The coolant gauge seems to flucuate between normal and hot.I changed the thermostat from a 195 to a 160 and changed the coolant sensor same thing.I am begining to wonder if the radiator cooling fan controller is bring the fan on when it is supposed to do they typically go out? expensive little bugger.

 

Leaking around the radiator cap looks like.