The Anti-Lock Brake Computer detected a problem, turned the system off, set a diagnostic fault code, and turned the yellow light on to tell you. Since the red warning light is on too, chances are there is no problem with the anti-lock system. The computer will turn the system off when there's a problem in the base braking system because it may not be able to function properly when there's a brake fluid problem.
First check the level of the brake fluid. You had to push the pistons into the calipers to make room for the new, thicker pads. Doing that would have pushed a lot of fluid back up into the reservoir, so if the level is low now, there's a leak. Check the parking brake to be sure it's fully released. If it is not, suspect a rear cable is rusted in the partially-applied position. Finally, if no other cause is found, did you ever push the brake pedal more than half way to the floor when working the pistons back out of the calipers to contact the pads? If you did, there's a real good chance the master cylinder was damaged. The lip seals can be torn on the crud and corrosion that build up in the bores where they don't normally travel. That will result in a low and mushy brake pedal or one that slowly sinks to the floor when you hold steady pressure on it. That internal leakage often doesn't show up for a few days after the damage occurs.
When you pump the pedal to run the pistons out of the calipers one side will always get there first and start to build hydraulic pressure before the other side does. Those unequal pressures will cause the pressure-differential valve to shift position and turn on the switch to turn on the red warning light. You may have inadvertently caused that valve to move not quite far enough to turn the light on, but it is now. On Chryslers and GMs that valve is spring-loaded to center itself when you release the pedal. On Fords it is not and they can be real frustrating to get centered again. I'm not sure if yours is spring-loaded or not, but to be safe, never push the brake pedal more than half way to the floor.
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Monday, February 25th, 2013 AT 12:22 AM