The cables are rusted tight and not releasing the rear brakes. Pull the release handle, then pull the parking brake pedal up with your foot or hand. The light will go off. If the pedal does not stay there, have someone hold it up. Put the car in "Park", then crawl underneath in front of the two rear tires, find the cables and flex them. If they're not rusted too badly, spring pressure will pull them to the retracted position. At that point, the cables will hold the parking brake pedal up and the light will stay off.
If the cables don't release or you're not sure, follow the cable's outer casing from the brake assembly inside the wheel forward to where the center cable comes out. The front end of the casing will be attached to the body at that point. If you look at the cable where it exits the casing, you might see a 1/2" long darker spot than the rest of the cable. This is the "witness mark" that shows the cable is not retracted yet. Keep flexing the casing, or you can try pushing the cable back in by hand.
You can prove both cables are retracted by stopping on a small incline, putting the transmission in "Neutral", and letting off the brake. If the car starts to roll, the parking brake is freed up. The two rear cables should be replaced. I have never heard of a sticking cable responding positively to lubrication.
This problem is much more common on Ford products, but can happen on any car.
Tuesday, March 31st, 2009 AT 2:34 AM