Check Engine Light and Clicking

I have a problem with my 89' Century 3.3. Just now, it starts clicking when I put in in drive or reverse and drive off, the check engine light also comes on then too. It makes a clicking noise until I turn the car off and back on. It sounds like its comming from by the alternator and power steering pump. Could this possibly be the transmission sensor? I plan on taking my car to a shop tuesday, but what could the problem be?

Maybe a bad idler pulley bearing or spring????
Try listening closelyto narrow down where it is coming from. Good Luck.