Tire pressure monitoring system algorithm for dual placard applications

The present invention relates to tire pressure monitoring systems, and in particular to implementing algorithms therefor. Still more particularly, the present invention relates to a tire pressure monitoring system algorithm for use with vehicles having dual placards for recommended rear tire pressures. A dual placard algorithm implemented in a tire pressure monitoring system which responds to tire inflation changes caused by the driver, and is thereby able to allow the tire pressure monitoring system to detect low tire pressure in dual placard applications. The algorithm automatically sets the threshold appropriate for a high placard pressure recommendation in the event the driver has inflated the rear tires to the high placard pressure recommendation. If the driver subsequently changes the rear tire pressure to the low placard pressure recommendation, the dual placard algorithm alerts the driver to manually enter a learn mode, whereupon the algorithm automatically re-sets the threshold to that appropriate for the low placard pressure recommendation only if the driver has deflated both rear tires to the low placard tire pressure recommendation.