bop11

If you have tire sensors, check the valve stems regularly. I went to air up and two tires had the end of the valve stem broken off. They did have plastic caps originally but the cap and stem end were long gone. The valve was still in the stem but a few threads of the valve were showing and the actuator pin was totally unprotected. Tire shops want to replace the whole sensor for $120 to $160 plus tire dismounting and remounting. The local dealer has replacement stems at $35 each plus installation of about $20 each. There is no need to replace the sensor itself. The GLK is a 2010 model and I don't think the stems were ever replaced so be aware that the stems do go even with plastic caps.

bop11

One other thought, if your 350 is more than 4 years old and you are going to replace some tires, stop off at the dealer and buy some valve stems and boots. Stem is 000-400-10-00 @ $43.75 each and the boot is 000-401-06-09 @ $3.70 each. Have these replaced when the tire is changed so you don't have a problem down the road. No need to change the sensor and they don't need to be reprogrammed. Cheap insurance compared with an aftermarket sensor @ $120 plus.