Geoff,

I don't know what PNP is but 1-2-4 is "Short circuit to ground in mode selector circuit". The mode selector has two signal wires, and a ground wire. The choice between W, E and S modes is made through the connection of either one or the other, or both signal wires to ground. If the TCM (transmission control module) registers that the signal is low in both signal wires simultaneously for at least 30 seconds, the DTC 1-2-4 is set. The cause is either a short circuit to ground, the W button has been depressed for more than 30 seconds or you have a defective switch. Why not try removing it, clean the switch and contacts using electronic contact cleaner and erase the code.