My problem is the caution came up on the dash so I went to check the tires. When I unscrewed the cap on one of the wheels, air started coming out and I couldn't stop it. I had to put air back in and screw the cap on to keep the pressure. When cap removed, air is let out again. Does the stem need to change or the whole sensor?

 

You might just need to replace the valve inside the stem.

Also, if I'm remembering correctly, the stem is separate from the pressure sensor. You shouldn't need to replace the sensor.

 

Discount Tire guy's well as others , will scan each TPMS unit to discern which , if and has low battery life remaining . And do it for free .

Then if you need replace any , I'd recommend the Tire Rack .com , then have install and balanced anywhere .

 

Worked perfectly.

 

Usually that means the valve core is gone. you might stop my a auto parts store or go to your local MB dealer and ask them if you can get a valve core. I have seen this happen a few times. If this still does not solve the problem. MB dealers have a hand TPMS scanner that will read how much life is left on each one! Hope that helps.

Ryan

 

You are correct. The stem itself is bolted to the sensor with T20 torx on the inside of the tire and a 11mm nut on the outside of the wheel.

Ryan