I Have W140 Mercedes Benz S320. Since I replaced left front wheel bearing, it sounds strange when the car almost stop.(when I apply brake n it is getting almost stop.) Someone told me that mechanic would be hit the wheel. so abs sensor or brake pad wear sensor is broken... I look forward to good advice. Thank you. John.

not normally it should be a couple of clips see this thread
http://www.benzworld.org/forums/w140-s-class/1585708-diy-replace-front-right-speed-sensor.html
seaming there is 1 per side

recheck brakes hard ware may also been bad , ck front wheel bearing also.

FUEL PRESSURE FOR S320 MERCEDES BENZ IS 46 - 52 PSI WITHOUT VACUUM APPLIED. 53 - 61 PSI WITH VACUUM APPLIED. 36 PSI RETENTION AFTER 30 MINUTES.

it sounds like your wheel bearings.jack the car up and spin wheels by hand and see if you hear any noise.

sounds like front wheel bearing going bad

prees the brakes and test the brake switch wire for power and u do have power there locate the brake module

The 1st thing to get looked at is the wheel balance.Have them checked.At the same time,if the tyres are o.k. have them rotated.This means you swap the tyres from the front to the back.Always keep the tyres on the same side of the car.So left rear goes to left front and the same on the righthand side.Also,a wheel alignment should be done.These are a tyre shop job.Cheap and doesn't take that long.If these don't correct the problem,the next thing to get looked at are the front wheel bearings.Get the tyres done 1st.This is the 1st step and also the most common problem.Hope this helps

Yes you can. Make sure you not gonna buy a ceramic pads. They are so loud. My own experiance.

Common causes for High-pitched noise from rear wheels are:

The wheel bearing: this is not usually dangerous in the short term, but I recommend contacting a mechanic and having it fixed. To test the wheel bearing, you lock front wheels, and jack up the car rear and spin the wheel (handbrake unlocked). If bearing is worn you hear a drone. When is the bearing, often car starts vibration above 40 mph.
Noise from bearing can be continuous, intermittent, only when steering, only when hot.

The brake pads: when brake pads are worn out they start making a squealing noise, in this case the noise is only when you brake or continuous. When you jack up the car the wheel may be a little stiff, but not necessarily.When brake pads are completely gone you also hear a scratching noise when braking. Inspect your brakes immediately.

Other suspension problems: Jack up the car as suggested above, check if the wheel has a slight play on the sides. Check all of the suspension components, suspension mounting points, and steering linkage for damage. Also, check the frame rail for wrinkles. It is very important that these components be in good condition, if you notice any problem here, go immediately to a mechanic.

Try doing the simple test above, reinstalling the wheel and working the tire back and forth. This is a common test for bad ball joints and wheel bearings.