Warning: External TPMS Sensors Could Ruin Your Towed Vehicle Valve Stems! Posted on February 15, 2014 by RobJuly 21, 2018 All automobiles in the US since 2008 are federally mandated to have a Tire Pressure Monitoring System (TPMS) and some vehicles had them as early as 1997. If you also have an aftermarket TPMS for your coach and monitor the … Continue Reading…