"Gear Select Problem" keeps appearing on the on board diagnostics dash.

When you first start the car "Gear Select Problem" comes on the dash and the shift indicator (P R N D 1 2) flashes repeatedly. When you shift into neutral or shift from overdrive to park, the shift indicator flashes again with the same 'Gear Select Problem' message. The car shifts into all the gears fine and drives fine, I'm wondering if the shift sensor or Neutral Safety switch could be at fault even though the NSS works fine; the car doesn't start in neutral.