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lou’s garage

Our plan was to take our 2011 Mercedes ML Bluetec to Florida and register it with Florida plates. To start the process, I needed a letter of compliance from Mercedes-Benz Canada, and that's where my problem began. The vehicle is not complaint with U.S. standards because the tire pressure monitoring system installed on the Canadian vehicles is different from the system installed on vehicles sold in the States. Mercedes-Benz Canada says that there is no fix for this problem. – Sam

Essentially, there are two common types of systems – tire pressure monitoring (TPMS), and tire pressure loss warning (TPLS).

TPMS employs a sensor in each wheel to monitor air pressure directly, usually providing the driver with current pressure readings.

TPLS exploits the vehicle's road wheel speed sensors to calculate tire pressure loss. As an individual tire deflates, the circumference of that tire also shrinks accordingly. This now-smaller tire revolves slightly faster relative to the others. The onboard computer will interpret the speed differential and conclude that a tire is losing air, subsequently turning on the dashboard under-inflated indicator. This system is also referred to as an indirect system, as the exact tire pressure is not known.

Your vehicle uses the latter system, which does not qualify for importation according to U.S. standards.

While there are after-market TPMS retrofit kits available, admissibility will still be in question, and you will likely not receive a compliance letter.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail, placing "Lou's Garage" in the subject area.

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