Tire Pressure Monitoring System (TPMS)
A (TPMS) Tire Pressure Monitoring System monitors a vehicle's tire air pressures and illuminates the amber TPMS light or audible chime to inform the driver of low or high air pressure. Some older model vehicles use an indirect system that utilizes the vehicle’s wheel speed sensors to estimate air pressures. This is based on the principle that a tire with low air pressure spins faster than a tire with high air pressure.
Vehicles built after 2007 are required by the tread act to include a direct TPMS system that includes tire pressure monitoring sensors placed inside each wheel assembly. The system includes a receiver located inside the BCM or keyless entry system, and an amber warning lamp. The sensors send a RF signal to the receiver including information like sensor id's and air pressure at regular intervals.
They include a lithium ion battery that can last up to ten years. As these batteries wear, they're less able to communicate with the receiver. The control module will illuminate the TPMS light if communication is lost. If the light is on continuously, check for manufacturer's recommended tire pressures on the driver’s side door sticker, and then inflate the tire pressures accordingly. These are the required values the direct system uses for that models tire pressures.
The TPMS sensor has a port to sense the tires air pressure. If the port becomes clogged, the sensor will indicate low air pressure to the module and the TPMS light will be illuminated. If the light is flashing, the system is indicating a system fault.
When the light stays on for only a few minutes of driving and then goes out, one of the tires could have low air pressure. As the tire heats from driving, the air pressure increases and the light goes out. This is because for every ten degrees of change in temperature, there is a one psi change in tire air pressure. Some liquid flat repair products can clog up the sensing hole in TPMS sensors.