On the front of each head is a Vacuum valve which connects to a module mounted on the front of the lower intake manifold. There are two metal rods (one for each head) which connects to that module. They are held in place with small plastic retainers which deteriorate over time and break resulting in the rods disconnecting and falling out or hanging loosely on the engine.

Replace those retainer bushings and it would possibly fix your problem as the ABS and Brake system both work off the vacuum of the engine.

Dorman makes replacements part #47099 but I would recommend trying the Ford OEM replacement as the Dormans fit loose and will fall out after a week or so.

The FORD Dealership wold love to sell you new ABS Module for $1100 and then tell you it still didn't go off. I took mine there I know, but I didn't fall for it. You would think a FORD trained technician would know the problem or know enough about brakes to check common low cost solutions ie. vacuum leaks and connections.

I don't know if Ford under-trains their techs or purposely with holds this information in hopes you will drain your pocket and eventually just buy a new car.

I've owned this 2003 Ford Windstar for a number of years and the ABS and Brake Lights have been intermittently lit for most of the time I've owned it. I've traced it down to a faulty Electronic Brake Control Module. Estimates at the dealership to fix are in the range of $600 - $1200. I could remove it myself and send off for repair for about $100, but removing the ECBM from this model is a pain in the ass. I've tried to get the unit off, but seems like it would require removing the entire Hydraulic Control Unit (HCU) along with the brake lines. Don't really want to do that. Definitely unsafe. My ABS does not appear to operate when the lights are on. Of course, this is yet another problem Ford knows about and does nothing about.