I have a 2002 Ford Focus ZX3 Zetec..My brake lights stays on while I'm driving or while the vehicle is in neutral/reverse. The only time the lights seems to work correctly is when the vehicle is in park. I've reviewed the electrical diagram for the vehicle and traced the brake lights wiring. Fuse #42 is the brake light fuse...which run a 15 Amp hot...to the left/right and third brake lights. My third brake light which runs through the hatch door was totally melted and burned out. I removed the light leaving the explosed wire to connect to a new light. According to the diagram each light hot is connect with a black (ground). Here's where it get interesting. Once I connected the black ground of the third light to the hot (green/yellow)...the brake lights goes off. This is while in Drive/Neutral/Reverse...but if I apply the brakes to test them it blows fuse #42..I've have totally removed all of the vehicle siding looking to see if one of the wires are exposed and touching. Nothing...Help!
If your car is equipped with electronic stability control, the brake lamp circuit works differently. Either way the stop lamps are controlled by the GEM module, the high mount stop lamp is not. With the stablity assist the module is connected to a relay and so is the high mount stop lamp. If the module is commanding brake lamps and you short the high mount stop lamp circuit to ground the lamps will go out. If you activate the stop lamp switch, the fuse will blow. So, that explains that part of it. Either the module is commanding the stop lamps, or the relay is stuck on. You can unplug the stability assist module to see if the brake lamps work properly. I am giving you the diagrams for the brake lamp circuit and the location of the module. I hope this helps, if so please accept this answer. If you need addtional help, just reply back to this answer and I will be happy to assist.
What exactly does the ESP module look like? I've been looking for the module. All can find located in the area show on the diagram was some wire harnesses that are plugged into another wire harness. I unplugged one and then the car won't start and non of the lights worked.
Is it under the fuse box? I don't know what I'm looking for...
It is under the fuse box and the cruise module, it is burried pretty good. I will attach a couple of pictures. The module is part of the brake hydraulic anti-lock unit. (#1 in the picture)