Where is the tcu for a grand Cherokee?

I do not believe there is such a thing as a tcu. there is an ECM (engine control module), and a TPS (throttle positioning sensor) TCU: Transmission Control Unit. On a Jeep Cherokee (not sure about the Grand Cherokee), it's located on the passenger side behind the dash. You can reach it from the bottom without removing anything, but it is easier of you remove the bottom of the dash.