The TPMS (Tire Pressure Monitoring System) is designed to measure air pressure and alert the driver when the pressure in one or more of the tires is below 25% of the manufacturer’s recommended pressure. There are two types of systems, direct and indirect. The far more utilized and more accurate Direct System uses sensors that are attached to each wheel. These sensors communicate with the vehicle’s TPMS module. The Indirect System typically utilizes the vehicles antilock braking system’s (ABS) speed sensors to monitor pressure.