Operation CHARM: Car repair manuals for everyone.

Principles of Operation

Principles of Operation
The Tire Pressure Monitoring System (TPMS) monitors the air pressure of all four regular road tires. The tire-mounted pressure sensors transmit via Radio Frequency (RF) signals to the TPMS module, using the valve stem as an antenna. These transmissions are sent approximately every 60 seconds when the vehicle speed exceeds 32 km/h (20 mph). The TPMS module compares each tire pressure sensor transmission against a set of low-pressure limits. If the TPMS module determines that the tire pressure has fallen below these limits, the TPMS module communicates this on the CAN network to the vehicle's instrument cluster which then illuminates the TPMS indicator and displays the appropriate message center message (if equipped).

The system is not affected by wheel and tire rotation.