Tire Pressure Monitor (TPM)
The tire pressure monitor (TPM) checks the inflation
pressures in all four tires at frequent periodic intervals.
The TPM’s sensors keep track of the tire pressures
both when the vehicle is moving and when it is stationary.
When the TPM detects changes in any tire’s inflation
pressure, it responds by triggering a warning lamp on the
instrument panel.
Each wheel is equipped with an electronic sensor assembly
located just behind the valve stem (Figure
42-12). This assembly is made up of a pressure sensor, a
transmitter and a battery. The pressure sensor measures
the tire's inflation pressure and relays this information
to the vehicle via radio waves.. These signals are picked up
by separate body-mounted antennas for each wheel A
central electronic control unit processes the signals from
the four wheels and reports any variations to the system.