Tire Monitoring System: Description and Operation
TIRE PRESSURE MONITORING: TIRE PRESSURE WARNING SYSTEM: SYSTEM DIAGRAM
HINT
Each tire pressure warning valve and transmitter sends information on the temperature inside the tire, the ID, and the tire pressure.
SYSTEM DESCRIPTION
1. DESCRIPTION OF SYSTEM
(a) Each tire pressure warning valve and transmitter is equipped with a tire pressure sensor and a transmitter and is installed in a tire and wheel assembly. The sensor measures the tire pressure. The measured value and transmitter IDs are transmitted to the tire pressure warning antenna on the body as radio waves and then sent to the tire pressure warning ECU and receiver from the tire pressure warning antenna. If the transmitter ID has already been registered, the ECU compares the measured air pressure value with the standard value. When the value is less than the standard value registered in the tire pressure warning ECU and receiver, the tire pressure warning light on the combination meter assembly comes on.
Tire pressure warning system transmitters with a different shape are provided for aluminium wheels. (They are not interchangeable with other wheels.)
2. INITIAL CHECK
(a) After the engine switch is turned on (IG), the tire pressure warning light comes on for 3 seconds and then goes off.
HINT
If the tire pressure warning light does not come on for 3 seconds, troubleshoot the tire pressure warning light circuit.
3. WHEN TIRE PRESSURE WARNING LIGHT IS LIT
(a) When the tire pressure warning light does not go off, or comes on while driving, check the tire pressure. If the tire pressure warning light comes on within several hours after adjusting the tire pressure, the tire may have a slow air leak. If the tire pressure warning light comes on even soon after adjusting the tire pressure, selection of the tire pressure warning switch (satellite switch) "MAIN" / "2nd" may be incorrect.
(b) Under the following conditions, the system may not function properly:
Areas, facilities or devices that use similar radio frequencies are located in the vicinity of the vehicle.
Devices using similar radio frequencies are used in the vehicle.
Large amounts of snow or ice are stuck to the vehicle, especially on the wheels and around the wheel housings.
A transmitter battery is depleted.
Tires and wheels without tire pressure warning valve and transmitters are used.
Snow tires or tire chains are used.
The registered set of the tires and wheels does not correspond to the selection of the tire pressure warning select switch.
If wheels other than the specified ones are used, radio waves transmitted from the tire pressure warning valve and transmitter may be affected.
A type of film that affects radio waves is attached to the windows.
Depending on the tire type, the tire pressure warning valve and transmitter may not function properly even if the specified wheels are used.
The system may not function properly unless it is initialized with the tire pressures at the specified values.
The tire pressure is abnormally high (absolute pressure: 600 kPa (6.0 kgf/cm2, 87 psi) or more; relative pressure: 500 kPa (5.0 kgf/cm2, 73 psi) or more.
(c) The average useful life of the grommet of the tire pressure warning valve and transmitter is approximately 10 years, at which time it must be replaced.
NOTICE:
Always use a new grommet, washer and nut when installing the tire pressure warning valve and transmitter.
(d) After removing and installing the ECU or a transmitter, check that no DTCs are output.
4. FUNCTION OF COMPONENTS
5. TIRE PRESSURE WARNING RESET SWITCH (SATELLITE SWITCH)
By operating the tire pressure warning reset switch, the tire pressure warning ECU and receiver can be set to issue a warning at an inflation pressure that corresponds to the type of tires.
Therefore, the warning threshold must be set to the proper value in order to comply with the local regulations.
Operate the tire pressure warning reset switch only after the inflation pressures of 4 tires have been adjusted on the vehicle.
To initialize the system, press and hold the tire pressure warning reset switch for 3 seconds or longer with the engine switch on (IG). When the system receives the initialization signal, the warning light blinks 3 times (1 second on, 1 second off).
During initialization, the tire pressure warning valve and transmitter measures the inflation pressure of the tires, and registers the signals that are transmitted into the tire pressure warning ECU and receiver at a frequency of once per minute. The initialization process is completed when signals from the 4 tires have been received.
Initialization is usually completed in 2 or 3 minutes.
6. TIRE PRESSURE WARNING SELECT SWITCH (SATELLITE SWITCH)
This switch is installed at the base of the driver side instrument panel.
The ECU can be used to register 2 sets of transmitter IDs, and can select one or the other using the tire pressure warning select switch. Consequently, there is no need to register the IDs again each time the tire and wheels are changed.
Make sure ID registration is performed by your car dealer.