open the right engine door that is from the seat, then stick your head in and follow the cable up to the plug, you will also need to drop down the dash to see the plug on the bottom right, this involves removing a few more small sections of panel work towards the cab to get at things, pull the plug open and check all the pin connections for green or burnt problems, its a good start with the next point to check involves removing the killer seat to get into the ECM under the left panel, you might also need to pop off the battery box to check out the fuse panel, the brake position switch runs on 24 volts but the transmission works on P.W.M. 5 volts pulsing, the waving of the display is often caused by the plug under the dash, any faulty wires should be pin out tested from the ECM plugs the wires are all numbered, when you get the wiring tamed if the transmission is still playing up I might have a few tips for you to find out what is knackered.