I just have new tires put on the rear and ever since then the Emergency brake light stays on all the time.

 

It's not just the emergency light that stays on, it can be low brake fluid, or maybe even a bad caliper that could be causing the light..i would check your brake fluid first.

 

The light is turned on by the pressure differential switch on the side of the ABS unit, where the two lines from the master cylinder connect. It indicate uneven pressure in the front and rear braking circuits. Could be air in the system, a leaking line, faulty master cylinder internal seals. If you have had any work done on the brakes, and bled them, it isn't unusual for the switch to "stick", and a few hard mashes on the brake pedal may be enough to break it free. If you haven't had the brakes worked on recently, you need to check for leaks.

 

My BRAKE light also just came home while driving, and I can obviously tell that there is less pressure in the rear braking circuit. Although there is not enough to make the calipers compress, when I unscrewed my bleeder valves on each rear caliper some fluid flows out only when the brake pedal is depressed. My e-brake seems to be operating just fine, and right now is my only means of applying rear brakes. I have not been able to find any leaks, and I have not serviced my brakes any time lately. I have also tried to "unstick" the above described pressure differential switch by mashing on my brake pedal, but to no avail.

Under what circumstances might the master cylinder internal seals fail, and do my symptoms seem to correlate with such failure? This problem seems too simple to be wasting my time, but I must be missing something (stranded w/o my shop manual), and any help is greatly apprectiated. Thanks everyone

 

i am having the problem with the brake light and the abs inop light also. took it to dealer to have the codes read, and they gave me, coo66 (rear abs circuit shorted or open, and c0078 (right rear solenoid open or shorted). the dealer told me to replace the abs module under the hood. i bought it and changed it today. still have both lights on and no rear brakes at all. can anyone please give me something to get me going in the right direction? does the computer have to be reset with this scan tool at the dealer or can i just pull the abs fuses and unhook the battery? i tried the later and the light still just comes on. thanks for any help. take care.