Nissan quest trans

Three months ago I had the transmission module changed due to the van wasn’t shiting to pick up power. then last night it is happening again I was driving at 40 miles per hour when I noticed the RPM Idle suddenly fell down then picked up as the car was to turn off. just minutes later when I stopped at the traffic light the van didn’t pick up speed until I changed from D to L drive and then shift again too D when picking up speed. I push on the gas paddle hard to get power but the RPM idle doesn’t go beyond 2 so the van pick up speed so slowly until I shift to L gear then D. What can be the problem the sensor module on the trans. or something else? - See more at: http://community.cartalk.com/discussion/2291509/transmission#latest