Hi
Take the wires off the motor block (making a note of which comes from which) put the block on the rails, apply power and use a multimeter and touch in turn, to the two pairs of red/blck wire points When the meter shows a voltage, that will show the two pickup wires. The other pins will be the return to the block from the circuit board. If my memory serves me correctly the two outer are the pick-up ones but I could be wrong!