I have a 2008 E320 Bluetec with 280,000 miles. I am getting a low tire pressure alarm when the tires are properly inflated. How can I know which tire has the problem? Do the sensors have a battery that needs replaced? Is the problem something other than a sensor? Does the spare tire have a sensor?

Sensors have a battery that requires you to replace the sensor over a period of time.

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Jim

Yes those TPMS sensors have a finite lifespan. There is a battery in each one.

To my knowledge there is not one in the ‘donut spare’.

Unfortunately the W211 (and the W164) sensors only report ‘good’ or ‘bad/battery dead’. So either fault trips the light. And they did not figure out how to display the values from the 4 corners on the dash. This was the first gen TPMS back from when they were first mandated so it was very crude by today’s standards.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Thank you for explaining (and showing) that sometimes the light doesn't go off before a test drive. The temp dropped about 20F today, and I got my tires refilled- but the light was still on. I've been afraid to drive the car. Now that I realize its part of the process, I feel better.




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