specequip, your truck has a short T2 to battery NEG. The card is doing it's job. The logic card needs some inputs; first on the list all control switches must close in a proper order, next the PMT circuit in the card is looking at the power circuit to see if any shorts are present T2 to POS and a bridge circuit in the card is comparing the voltages T2 to POS with T2 to NEG. When the KSW is turned on these voltages should both be 18 volts with a 36 volt truck. To confirm T2 to NEG will be the other half of the remaining 36 volts.