I have a 2003 Ford Explorer 4x2 V6. I have been having intermitent trouble with the shifter locking up in park. A guy told me yesterday my break lights didn't work. Definate connection. When break lights work, shifter works. When break lights don't work, shifter doesn't work.

I checked the break light bulbs and fuse. Both OK. Is there a relay problem or something else?

 

Look at the brake light switch on the top area of the brake pedal. The connections on Ford's swirches are a very weak point for failure.