Rear head rest removal

I have a 2008 Mercedes E320 did a brake job on it and put wheel bearings in the right front but did not change out the hub and now the ABS light and the triangle warning light comes on but it throws no codes, I tried taking out the ABS sensor squirting brake fluid in and air to clean up maybe the hub but made no difference.

I'm not positive, but the rear head restraints cannot be removed, as they form part (along with the windshield header) of the occupant protection when you roll it. They should pop up when you tilt beyond a pre-set angle and can be lowered and raised but probably not removed.