Recently my '09 has had completely unresponsive brakes shortly after starting the car. Then all appears well after that (I hope). The pedal goes down, you sort of crap your pants, and then after a few feet the wheels lock up.

Brake fluid is fine - level is at max.

Any ideas what this may be? Doesn't feel like hydraulics to me. Almost like ABS doesn't allow brakes to lock because it thinks the car is in motion.

Hydraulics, they often do that. You would feel the ABS kicking in through the pedal. ABS doesn't let the pedal drop to floor either.

Don't drive the car, you are in a danger situation.

When it happened I held the pedal to the floor and after a while the wheels locked up. No brake pumping. That's why I think not hydraulic, master cylinder, etc.

Mechanic just called and said there's a code for rear wheel speed sensor "erratic". Said it wasn't even an actual code, just sort of a message. $337.00CDN too!

mac , that does indeed sound hydraulic , why don't you tow it in for a FULL brake FLUSH / BLEED , then see if anything "weird" - sinking pedal , your symptoms still evident , locking up too soon etc. Good luck G. 2/22/2018

If the pedal is dropping more than normal then you have a hydraulic issue, you either get that or you don't. NO pedal should be going 'to the floor'.

' Almost like ABS doesn't allow brakes to lock because it thinks the car is in motion.'

Uh, what it is supposed to do yet you speak of that as if it were a problem. Brakes are NEVER supposed to fully lock up with working ABS.

When I said "to the floor" I didn't mean the floorboards. I just depressed the brake pedal completely and held it there. Nothing happened, then they kicked in.

Uh, what it is supposed to do yet you speak of that as if it were a problem.

amc49 - Of course that's a problem. What I said was that I held the pedal all the way down and the brakes did nothing for about 15 feet. Then they kicked in - no pedal pumping. Something stopped the brakes from engaging.

As we know ABS releases brakes alternately when the car is in motion and lockup occurs. Almost exclusively on slippery ground. I personally have never got ABS to kick in on dry pavement. The purpose of ABS is to keep the car going in a straight line. Arguably it makes the car stop sooner than it might have without ABS. To function properly the car must sense both lockup and motion simultaneously. But if the motion sensor were to behave erratically, the ABS system could (perhaps) continue to release the brakes prior to lockup/full-stop even when stopping slowly on dry pavement. I believe that is what happened to me.


Rear ABS sensor has been replaced so hopefully that is the end of this issue. I'll update here if not.