Auto transmission shifting hard

I have a 98 Z24 with the 4spd auto. trans. I few days ago the ETS light on the dash started coming on and off at random intervals while driving (engine light also comes on). When this comes on, the trasmission shifts way too hard, and almost feels like its going to jerk the motor out when going shifting frompark to rev or drive. After ir goes off, it shifts fine. I know there is a TV cable on other cavaliers that controls the line pressure to the trans, but I dont see this on mine. Any ideas?