For John,
Please check this out: I'm betting that "I'm Right" is correct, and since
you didn't DO anything that we know of to cause this to start (if you DID do
something, like install a stereo, or wire up a trailer plug, or something
else, then speak up now and let us know!), then I'd check to see if you have
any dual filament bulbs in your brake light system. These would be 1157's or
equiv - where the same bulb has two filaments, one for tail lights and one
for brake lights. Often, one filament will break and bridge the other one,
and thereby transfer power into that circuit. How do I know this? Experience
is a hard master.

If you find a bulb that doesn't look right, replace it with a new one.
They're cheap.

I'm not sure if your Rodeo has bulbs like that - some are all separate 1156
bulbs, which only have one filament per bulb, IIRC... but it wouldn't hurt
to pull all the bulbs and look at them. Most of the newer cars use a
separate, 1-filament bulb for turn signals, and that shouldn't be involved
here, but I could be wrong.

If you find the problem, please post here and let us know what it was.

Steve