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ABS trying to engage

I have a 2005 Hyundai Santa Fa 4 wheel drive. I bought it used a year an a half ago. It has 106, 580 miles. Since purchasing I have had problems with the ABS wanting to engage when I am braking at low speeds. It doesn’t always happen, seems worse when first starting in the morning and when the weather is wet/humid (?). I can feel something in the brake pedal, tap it lightly to disengage. No warning lights come on. I took it to the dealer. They did a diagnostic and showed nothing wrong with the ABS, however they said I needed rear brake rotors. They replaced pads and rotors. In the process the caliper bolt seized and needed to be extracted by a third party.

When I picked up the car the mechanic said the brake line was very dirty with lumps in it and should be flushed soon. Driving away from the dealership I still had the same problem with the ABS. They told me to have the brake line flushed. The dirt and lumps could be causing air pockets which is making the ABS think it needs to engage when the system does its self diagnostic test.

A week later I had the brake line flushed. The ABS system continues to try to engage. I know I needed brakes and the brake line flushed but I still have my original problem. Now they have me scheduled to drive with a Hyundai technician to see if he has any idea of what the problem is and how to fix it.

Has anyone had this problem and what was the fix?

Have someone check the wheel speed sensors and the sensor tone rings for debris. Brake dust can accumulate on the sensors and tone rings where it sends false signals to the ABS computer causing the ABS to engage at slow speeds. Also have them check for rust under the wheel speed sensors which can cause them to become misaligned to the tone rings which can cause the ABS to engage at slow speeds.