I have a 2011 F-150 XLT, 5.0 that I've owned about a year. Twice in the last week the Brake Malfunction light came on and the message panel read "Check Brake System". The brakes were working fine and everything checked out OK. The light went out after shutting down the truck and restarting. The only thing I've done to the brakes was to bleed and flush the system about a month ago. I used a vacuum pump at the wheel cylinders. In the past I've always used an assistant to pump the pedal but used the pump this time.
Has anyone a bit of wisdom on this?

 

Are you sure the brake fluid isn't low? Are you sure the parking brake is completely disengaged?

 

These are the 2 first things to check.

Also check that you didn't knock the FLI connector lose while working on it
(FLI = Fluid Level Indicator... the switch in your brake fluid reservoir)

If these all check out OK you will need someone to pull the codes. It could be indicating an intermittent failure in the ABS/ESP system. If it is a minor failure it will reset on a power cycle and then it might re-occur if the same scenario is repeated.

 

Fluid level is about 1/4" below MAX, parking brake is fully released, FLI connection is tight and no codes shown when scanned. The light has only come on when steady driving, not during braking. It does reset with a power cycle. Braking does not seem to be effected.

 

Any one else out there that might have an idea?? Even if it something from "out in left field", I'm open to any possible solution!

 

I would reflush via pedal, and I wouldn't wait till the pedal hits the floorboard to close. I bet there is a air bubble trapped inside there.

 

how are you scanning for codes? Some scanners may not check all codes.

If the ESP is turning on the light, it should have a code stored.

It is highly unlikely that this is caused by an air bubble.

If I were a betting man, I would place my money on an issue with a Wheel Speed Sensor... perhaps your air gap on one of them is slightly off and it sets a plausibility fault if you drive long enough in a straight direction. Does this only happen when driving straight and/or on a highway?

You could also check your tire air pressure... is one low? Are your tires all 4 matched or did you replace one? If you somehow have 1 tire with a different rolling radius it would change the wheel speed signal from that tire.

 

I bled the brakes again the old way and got a few bubbles showing up. I drove the truck the same route the the light came on twice.. No warning light now and the pedal seems a bit higher.
Thanks to all that replied with suggestions!!

 

I'd check your wheel hub assembly. Make sure the ASB sensor or the line isn't damaged or unplugged. If that isn't making a connection you'll get that error too. It's worth a shot and easy to diagnose.

 

had the same problem, researched the **** off this one; turned out to be the ABS module. Replaced it, got it flashed and all's well.