2010 Focus---ABS locks up LF wheel

 Vehicle Data2010 Ford Focus SE

• VIN  1FAHP3FN3AW186978
• Mileage  110,000 mi
• Engine  2.0L / 4 cyl / Gas

Concern--

When abs is activated on a slick surface the LF wheel locks up and does not release until you come to a complete stop, Also there is some RR brake activation but it does not lock up.

Also when you get the abs to activate, you can take your foot off the brake pedal and it contintues to keep LF wheel locked up until you reach a stop

Under normal braking conditions there are no problems, it stops normally and braking is even from side to side.

Graphed all the scan data and recorded it, and whats noticeable is every pid freezes for a few seconds when this is occuring, like its in some sort of logic lock. All four wheel speed sensors will slowly ramp up as I speed up and when I get the abs to activate the pids will all freeze and when it finally comes to a stop everything begins working again. Wheel speed signal will be 40mph in 1 frame of recording and then the next frame its 1 mph.

I have scoped wheel speed signals, and they all look normal. I cant make any sense of it, so I tried a used controller and HCU.----NO Change

I Scoped powers and ground when this occurs, and they are normal.

Anyone seen this before?

Thanks,

Mike Paxton
Rum River Automotive
Princeton, MN

YES THAT IS BAD should make sure all bakes and cylinders are good and clean all sensors . are all tires the same size ?. you say you tried differ module and a b s unit . I would rather pull the fuse and not have it GOOD LUCK

I would disable the abs system, hard brake it a few times on the road, then get it in and see if that weel is difficult to turn.
Every instance of a locking wheel I have encountered so far has been a mechanical issue with the caliper or hose.
If it isn't hard to turn with the abs disabled, then I'd start barking up the abs tree.

Thanks for all the replies guys. To be clear, this is not a mechanical brake problem. When abs is disabled the care drives normally, I can stab the brakes on ice and lock up the wheels and when off the pedal they let go instantly.

Everything mechanical checks out fine, This some sort of abs control issue

Thanks for the help!

That is some strange stuff going on there.
I was wondering if someone may have repaired brake lines and got them mixed up at the master or the ABS unit, but that doesn't explain all the data PIDs freezing.
Have you tried exercising the bidirectional controls with the car on the rack to verify that the unit is controlling and releasing the 4 corners as commanded? I don't know what it may prove or disprove, just spot balling.
Very curious, I have never had a car in my bay with that problem.