I have a 2006 Town Car that cranks but will not fire. Fuel pressure ok. Flashing security light during crank and non start. Disconnect battery, reconnect and start is normal, however when the heater is turned on the car flashes two symbols on the instrument cluster briefly (less than a second) showing over temp and open gas cap. This flashes regularly about every 4 seconds until the heater is switched to the off position. Weird. Any suggestions?