Tire Monitoring System: Description and Operation
System DescriptionTPMS Control Unit Inputs and Outputs for 20P Connector:
System Structure
Once the vehicle speed exceeds 28 mph (45 km/h), the TPMS control unit monitors all four tires and the system. If it detects low pressure in a tire, it alerts the driver by turning on the low tire pressure indicator. If it detects a problem in the system, it turns on the TPMS indicator.
Control unit
Mounted in the middle of the dashboard, the TPMS control unit receives pressure sensor ID signals every time the vehicle speeds exceeds 28 mph (45 km/h). It also receives signals from the transmitters for tire pressure and the sensor condition, and it continuously monitors and controls the system.
Indicators
Two indicators are in the gauge control module: The low tire pressure indicator comes on when any tire pressure is low, and the TPMS indicator that comes on only if there's a problem with the system.
The low tire pressure indicator alerts the driver that a tire(s) pressure is low, but does not specify the tire(s) location.
Tire pressure sensor
Each sensor is an integrated unit made up of the tire valve stem, a pressure sensor, and a transmitter. The unit is attached to the inside of the wheel, around the valve stem. The sensor transmits the internal tire information to the control unit once every 60 seconds when the vehicle speed exceeds 28 mph (45 km/h). When the TPMS control unit receives a tire pressure signal that is less than 168 kPa (1.7 kgf/cm2, 24 psi), the control unit then turns on the low tire pressure indicator. When that tire's pressure is increased to more than 190 kPa (1.9 kgf/cm2, 28 psi), and the vehicle is driven above 28 mph (45 km/h) the transmitter sends the tire pressure signal to the control unit, and then the control unit turns the indicators off.
Do not mix the tire pressure sensor with another TPMS type.
Sensor active:
^ When the wheel starts to rotate, the sensor detects the momentum, and switches the sensor to the normal function mode.
^ The LF (low frequency) signal of the TPMS initializer tool makes the sensor active even though the vehicle is stopped. Sensor inactive: When the acceleration sensor detects the wheel is stationary for 5 minutes or more continuously, the tire pressure sensor shuts off automatically, and changes to sleep mode.
Wheels
TPMS will not work unless TPMS type wheels are installed on the vehicle. The original equipment wheels have a "TPMS" mark (A) on them and counterweights (B) cast into the opposite side of the spoke to counter balance the weight of the tire pressure sensor (C).
System Communication
^ When the vehicle is traveling more than 28 mph (45 km/h), an RF (radio frequency) band wave signal is continuously transmitted from each tire pressure sensor to the control unit.
^ When the wheels rotate, the tire pressure sensors' momentum is detected, switching them from sleep mode to normal function, mode. After the vehicle is stationary for 5 minutes, the sensors switch from normal function mode back to sleep mode to extend their battery life.
^ Each tire pressure sensor has its own ID to prevent jamming by similar systems on other vehicles. After memorizing all the sensor IDs, the control unit receives only those specific signals.
^ An cannot be memorized automatically. The control unit knows which ID belongs to each tire pressure sensor. This recurring ID confirmation prevents any confusion in the system as a result of doing a normal tire rotation.
