check engine light

Have 2001 Taurus. Recently, during a cold snap, my engine lite came on. When I turn the head lights on the engine lite goes off. I have an OBD II reader and there are no hard codes. It does, however, indicate several sensors have not finished diagnostics. One recommendation was to disconnect the battery for 10 minutes, touch the battery cables to ensure a complete discharge and then reconnect. Same situation, check engine lite comes on and will go off when you turn on the headlights. Ran another diagnostic, no hard codes, only the incomplete sensor diagnostics - there are no codes indicated at all. Baffled? Has 105K and I take very good care of it. Runs great and condition has not affected performance.