E4 U12 code on dash won’t start

[Gkbru]

All almost fixed.. Tractor runs no error codes. Main fix was a 5 amp fuse. Was call out as a controller switch. This got the 12 volts to the shuttle shift FNR proximity switch. It is a npn proximity. So normally open when in gear. It is basically an inductor with a npn transistor in it. Will post later how to trouble shoot such a switch. Other issue I don’t quite get that the bracket that holds the switch is not quite adjustable enough to the inductor over the metal arm on the shifter worked before . It’s off about 1/8 inch. This close the switch and sets the voltage from 7.2 volts to zero indicates neutral for the controller.
thanks for everyones help

 

[Gkbru]

Here is how to check the proximity switch on a shuttle shift lever. Unplug the cable to the switch. Run 12 volts to pin 1 or A from the battery. This will be the red wire on NH. Connect the black wire to ground. I used the mounting bracket of the switch. This is pin 3 or C.

With a meter go between ground and pin 2 or B. When the lever in in forward or reverse the meter will show open. When in neutral and the metal tab is over the plus symbol and no more a 1/16 inch away from there will be continuity between pin 2 or B and ground.

i also checked on bench as I am Ham and have a 13.8 volt power supply. i wired up the positive to pin 1 and negative to pin 3. Used a plier to make contract on the + symbol with meter between pin 2 and negative of power supply. You can see it closing and opening as you move the pliers.
what this is doing is using the inductor to make the transistor turn on and off. From the collector on 12 volts and emitter grounded.
The 7.3 volts in on the base from the controller is what the tractor sees when in gear as the npn transistor is open..