Anti Lock Brakes

Hi,

I have a 99 F-150. The truck has about 133,000 miles on it. I changed the brake pads all around the truck back at about 50k miles. Before I changed the pads out, the ABS light came on. I read where it could be that I needed to add some ABS brake fluid to the reservoir and that should make the light go out. I filled my reservoir back up to max fill line, it was about 1/16" below the line, but I went ahead and filled back up to the line. Since then, I have been reading that it could be a sensor problem and heard that it would cost a lot of money to fix. I also read somewhere that I could take it to Autozone and let them put their computer on the OBDII port. I went there today and asked and they said it was a dealer item. I was wondering what the sensor looks like and where I can find it on my truck. Is there one for all 4 wheels or just the front ones? My invoice said it has 4 wheel ABS. I am going to assume that I have 4 sensors but am not sure. Please clarify and let me know what else I can try to fix the light. I have been driving it every day without any problems. I am also aware that I won't get good traction on snow, ice, or wet pavement.

As far as i know, thee should only be one sensor for the abs that monitors all 4 wheels....diagnosis of the trucks computer tells which
one(s) need the help.

The job can be expensive depending on what needs to be done, but considering how important your brakes are to the vehicle, don't you think it's worth getting the problem fixed? Speaking of which, if you haven't done your brakes since 50k miles and you're now at 133k it's probably worth getting them done again anyways, so do it all at once is my advice.

Try this before you go through the extra expense. There is a bleeder valve on the ABS control unit. When you put the new pads and shoes on, the calipers and cylinders were compressed. This put a lot of fluid backwards through the system. A piece of debris may be blocking the sensor port.

Bleed the ABS, fill the reserve, then bleed the right rear wheel and see if the light goes out. Do the bleeding with the engine off, but the key on. If the light does not go off, bleed the left rear, then the right right front wheel. If this does not put the light out, the sensor is located on the unit. Replace the sensor first. It cost under $30.00. Just remember, just because the ABS light is one, does not mean that you do not have brakes, just that the ABS system is not working.

4 wheel has 2 sensors in the front and one in the differential.usually the one in the differential.also when the ones in the front are bad, it's from a loose hub.
the abs pump and module are together on the left front fender well,under the air filter housing.look at the pump motor there will be 2 wires going to it.if there is corrosion at the wires they go into the motor, that is your problem.
unfortunatly the pump will have to be replaced.