Be sure the battery is ok and charging system out put is good. If it was the directional switch you would either get no code or get a P-22 or F-16 code. Since you are getting reverse with no code and only coding while in forward then the switch is doing it's job. Very possible you have a forward coil gone south, open wire related to circuit, VCM issue or possibly a meter panel issue. Be sure to check for corrosion in connectors and moisture.