my transit does the exact same thing jay and has been doin for the last 3 years ,never had it looked at so if you get it fixed would you post the fix up here .
all i do when it happens is turn the key back one notch and back to the on position and the light goes out .it happens on mine when you lift your foot off the throtttle when you are preparing to stop.so it makes me think it may be a throttle /accelerator pedal.my van is 03 and 60,000 miles.

cheers james