2005 Civic automatic downshifts in high gear
 

I have a 2005 Civic automatic and within 3 miles of driving it on the highway it will downshift into a lower gear. I can get rid of this by stopping the car and turning the engine off, but when I restart it the gear shift will get stuck in park and I have to stick a screw driver in the hole to free it. Once this happens (and it is more frequent when temperatures are colder outside), it will not happen again unless the car sits for a long time.

Re: 2005 Civic automatic downshifts in high gear
 

This sounds like it COULD be related to the transmission range switch. Have you noticed if the D light on the dash disappears when the car acts up? Does that entire set of lights work correctly when the car acts up?

If not, then that explains both symptoms. The ground wires for that switch are attached to a 10mm bolt, right beside the upper radiator hose on the engine. Make sure it is tight and the wires are intact. If that's ok, then further diagnosis is needed.