I got a 94 22re pickup and it just started turing the marker lights and the dash lights while i hit the brakes, even with the car off it does this. I had a harness for towing originally hooked up and thought the problem might of been related to this so i removed it and still it still does this.

Any suggestions or ideas would be great.

 

Does it do this with the lights on also?
Do the brake lights work?
Do the turn signals work?
Do the marker lights work? (come on when you turn on the lights?)
Did you disconnect or rewire anything for the tow plug?
Did you rewire anything in the dash? Stereo, some accessory?)

First thing I would check is the brake light bulbs/sockets. Pull em, clean the socket, clean the bulb base. Maybe just pop in a new bulb for a test (they're cheap.)

 

Check for a grounding or corrosion problem at the light in question. Usually it's the 4 to 3 towing adapter has gone bad...

 

Likely a bad ground. Why? Because the marker light and the brake light are the same light bulb (dual filament) and share a common ground connection. If the ground connection is bad, one filament can find a path to ground through the other filament. Hit the brakes and the brake filament grounds through the marker filament and you get what looks like a marker light (dim vs. the bright brake light). Turn on the parking lights and you'll probably find if you hit the brakes, the light goes out all together. Why? You have 12V on both sides of the lamp, i.e. both filaments are at 12V, no voltage difference, no path to ground and no light.