Got a 96 ford ranger 4.0 .check engine light came on.?

.replaced the pcv valve and the hose on it.started it but check engine light was still on.then i bagan to chack everything.oil is fine and up to level.but i noticed coolant was a little low.even when running it still wouldnt come up to the radiator neck at the cap.could this coolant problem be the cause of the check engine light to come on.