Universal Tyre Pressure Monitoring System with 4 External Sensors The MT-S4 is a wire-free tyre pressure monitoring system for cars, SUVs, vans and light trucks. Four external screw-on sensors transmit real-time pressure and temperature to a solar-powered dash display, so drivers read live tyre pressure without opening the door of a workshop. Where a simple warning light is not enough, this tyre pressure monitor shows the exact psi of each wheel and sounds an alarm before a