Hi Guys

I am working on a 2004 aviator 2wd that the abs ratchets on during a normal stop. No codes and all the wheel speed sensors read correctly and match. What happens is the pedal will fall and then hit back up like the abs is ratcheting.

Thanks in advance for any and all help

 

Does it do this at every stop? How old is the battery? Does it do this immediately after pressing the brake pedal, from any speed, or is it only when the vehicle gets below a certain speed? The symptom you describe is consistent with the pump kicking in, I'm wondering if a weak battery combined with the load from brake lights is causing the pump to basically do a power on self test. I'm not totally sure the system does this, but it sounds like exactly what happens when I activate the pump with my scan tool while holding my foot on the brake pedal.

-Rod

 

very similar to activating the pump with a scan tool. It only does it at low speeds, intermittantly, and the battery is good. We did figure out what was wrong, the rear end has a slight howl, and every once in a while, the rear sensor would miss read. Pulled rear diff apart and the bearings are junk letting the ring gear move side to side.

 

Wow, that's good information. I'm sorry you had to be the one to find it.

-Rod