Stoplight bulb=ABS light
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Joined: Aug 2004
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Stoplight bulb=ABS light
I just replaced a burned out brake light and it corrected the problem I was having with my ABS light coming on. 91 aerostar, ABS light would come on at about 37 MPH, and stay on until the engine was turned off. The right rear brake light was burned out and when replaced, the problem was corrected. I put back the old one to "double check" and sure enough.......37 MPH and light came on. I put the new one in and now, no problem. Anyway, just for anyone's information........Nick
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Joined: Sep 2003
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From: SoCal
Originally Posted by roree
The abs and cruise control use the brake light filiment as a ground path. No filiment and the systems don't work.
The ABS does a diagnostic when the ignition switch is first turned on. One of the things it checks is continuity through the brake light circuit. If the bulb filaments are out, the diagnostic fails, so the warning light comes out. The ground path is part of the circuit to be sure.
Similarly, the cruise control also uses the brake light circuit to switch control on and off. If it sees that error condition, it will not work either.
Similarly, the E4WD and torque converter lock-up controls need to have the brake system functioning for them to work. (They use the brake light circuit to de-activate their functions when the driver applies the brakes.)
