Transmission will sometimes not want to shift past 1st

I have been having problems for the past couple
weeks involving the transmission. The Jeep will
sometimes not want to shift past first gear. I can
remedy this short-term by putting it into 4 wheel
drive or by revving up the RPMs past 4,000. The
check engine light does come on but will go off
after a couple of days when the problem hasn't
occurred. The issue will occur about once or twice
every 3 to 4 days. Could this be an output sensor?