As the title says, , just came on, got no idea what caused it, manual calls it a emissions warning light, so since there is no diagnostics , can anybody point me as to what to check ?

Truck runs fine, the only thing that happened recently was it lost 2 fan belts, and i just replaced them , other than that all else seems to work fine.

I did disconnect the battery for a couple of hours. no change, If truck sits over night, the light does not come on immediately, usually after warm up, but stays on the rest of the day, evven if i shut the truck off for a while.

 

BTT please !