From my reading of the manual, page 44-14,the transmission temp is measured at the cooler not at the transmission, and is measured by a probe that is inserted in the RH end of the cooler with a connector into the circuit. According to the manual page 44-15 there is no item on the EAT ECU...

My vehicle, same MY as yours has the same problem after 275K/kms. The squab is available as a genuine part, about $450 Australian. One way to minimise the sore bum or back is to tilt the back of the seat so you are in more of a straight arm position. Winjeel