Athearn Genesis SD70s came factory equipped with a Digitrax designed light board. The board is NOT a DCC decoder. If you want to add a decoder and have alternating ditch lights the following steps are recommended:
1 - Remove locomotive shell;
2 - Remove dummy nine pin plug from wire harness and insert Digitrax DH163D on the harness;
3 - Remove the wires of one of the ditch light bulbs from F1N and F1P and solder them to F2N and F2P;
4 - Program CV51 to 106, CV52 to 107 and CV63 to 40.
5 - Reinstall locomotive shell.
F2 on your Digitrax throttle will now activate the alternating ditch lights when pressed.