Tire Pressure Warning System (Diagnostics - Introduction): Overview Scion xD I

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1. TIRE PRESSURE WARNING SYSTEM PRECAUTION When the tire pressure warning light turns on, immediately check the tire pressures and adjust them to the specified value. (The tire pressure warning light will come on after blinking for 1 minute if there is an open in the tire pressure warning light circuit.) Cold Tire Inflation Pressure Tire Size Front Pressure Rear Pressure 195/60R16 89H 230 kPa (2.3 kgf/cm 2, 33 psi) 230 kPa (2.3 kgf/cm 2, 33 psi) When the tire pressure warning light turns on after blinking for 1 minute, there is a malfunction in the system. Check for DTCs. It is necessary to register the transmitter ID in the tire pressure warning ECU after replacing the tire pressure warning valve and transmitter and/or tire pressure warning ECU. Refer to «REGISTRATION»(ref-388778-S13930534572011031100000). When replacing the tire pressure warning ECU: Using the Data List, read the transmitter IDs registered in the ECU and make a note of them before removing the tire pressure warning ECU. Register the transmitter IDs after installing a new tire pressure warning ECU. When replacing the tire pressure warning valve and transmitter: Take a note of the 7 digit number (transmitter ID) written on the new tire pressure warning valve and transmitter when replacing the old one. Register the transmitter ID in the tire pressure warning ECU after replacing the tire pressure warning valve and transmitter and installing the tires and wheels on the vehicle. NOTE: The transmitter ID is written on the tire pressure warning valve and transmitter. It will be unable to be read after installing the tire pressure warning valve and transmitter on the tire and wheel. Therefore, take a note of the transmitter ID before installing the tire pressure warning valve and transmitter. When replacing the tire pressure warning ECU and the tire pressure warning valves and transmitters: It is necessary to perform initialization. Refer to «INITIALIZATION»(ref-388778-S04025604892011031100000) after the registration. Refer to «REGISTRATION»(ref-388778-S13930534572011031100000). Precautions about the tire pressure: The tire pressure decreases naturally. In winter, tire pressure may decrease due to low ambient temperatures (tire pressure decreases by approximately 10 kPa (0.1 kgf/cm 2, 1.45 psi) for every 10°C (50°F) drop in the ambient temperature). Therefore, the tire pressure warning is more likely to operate if the tire pressures are not adjusted appropriately. If the daily temperature variation is large, pressurize the tires high so that the tire pressures are suitable under cold conditions. As a result, incorrect tire pressure warning operation should decrease.
2. IN CASE OF TIRE AND WHEEL REPLACEMENT When tires and wheels are replaced, always ensure that each transmitter ID is correctly registered.
3. INITIALIZATION PRECAUTION Initialize the tire pressure warning system after any of the following is performed: Replacing the tire pressure warning ECU and/or the tire pressure warning valve and transmitter Rotating tires on vehicles with differing front and rear tire inflation pressures. HINT: The tire pressure warning system will not operate properly if it is not initialized. Refer to «INITIALIZATION»(ref-388778-S04025604892011031100000).
4. FAIL-SAFE FUNCTION When a system malfunction occurs in the tire pressure warning system, the tire pressure warning light comes on after blinking for 1 minute and informs the driver of the system failure. The result of this diagnosis is stored in the tire pressure warning ECU.
5. CHECK TIRE PRESSURE AFTER REPAIRS After repairs, confirm that the actual tire pressures are displayed in the Data List. Refer to «DATA LIST / ACTIVE TEST»(ref-388778-S18118133212011031100000).

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The tire pressure warning valve and transmitter sends information on the temperature inside the tire, the ID, and the tire pressure.

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1. DESCRIPTION OF SYSTEM Each tire pressure warning valve and transmitter is equipped with a tire pressure sensor and a transmitter and is installed in each tire wheel. The sensor measures the tire pressure. The measured value and transmitter ID are transmitted to the tire pressure warning antenna and receiver on the body as radio waves and then sent to the tire pressure warning ECU from the tire pressure warning antenna and receiver. 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, the warning light on the combination meter turns on. The tire pressure warning reset switch addresses the differences in the air pressure settings by the type of tires.
2. INITIAL CHECK After the ignition switch is turned to ON, the tire pressure warning light turns on for 3 seconds and then turns off. HINT: If the warning light does not turn on for 3 seconds, troubleshoot the pressure warning light circuit. Trouble Area Proceed to Tire pressure warning light circuit Refer to «Tire Pressure Warning Light Circuit»(ref-388779-S32976892252011031100000)
3. WHEN TIRE PRESSURE WARNING LIGHT IS LIT When the tire pressure warning light does not go off, or when it turns on during driving, check the tire pressure. If the tire pressure warning light turns on within several hours of adjusting the tire pressure, the tire may have a slow air leak. Under the following conditions, the system may not function properly. Facilities or devices that use similar radio frequencies are located in the vicinity of the vehicle. A radio device of similar frequency is used in the vehicle. A large amount of snow or ice is stuck to the vehicle, especially onto the wheels and around the wheel houses. The battery of the sensor has been depleted. Tires without a tire pressure warning valve and transmitter are used. Tire chains are used. If any wheels other than the specified ones are used, the system may not function properly because interference may prevent the radio waves from being correctly transmitted from the tire pressure warning valve and transmitter. A type of film that affects radio waves is attached to the windows. Depending on the tire type, the system may not function properly even if the specified wheels are used. The tire pressure is abnormally high (absolute pressure: 600 kPa (6 kgf/cm 2 , 87 psi) or more; relative pressure: 500 kPa (5 kgf/cm 2 , 72.5 psi) or more). The average usage life of the grommet of the tire pressure warning valve and transmitter is approximately 10 years, at which time it must be replaced. If a tire pressure warning valve and transmitter is removed from a wheel, replace the grommets. After removing and installing the ECU or a sensor, check for a diagnostic trouble code and verify that it is a normal code.
4. FUNCTION OF COMPONENTS Components Function Tire pressure warning valve and transmitter Combined as a single unit with a disc wheel air valve, it measures tire pressure and temperature and transmits an ID number for measurement values and identification. Has a built-in battery. Tire pressure warning antenna and receiver Receives signals from a transmitter and sends the signals to the tire pressure warning ECU. Tire pressure warning ECU Receives the signal from the receiver and identifies it as the vehicle's own signal. If the measured value is equal to or lower than the specified value, it transmits a signal so that the tire pressure warning light on the combination meter turns on. Tire pressure warning light Located in the combination meter, it informs the driver of lowered tire pressure and system failure. Tire pressure warning reset switch Enters the initialization mode for tire or wheel replacement.
5. TIRE PRESSURE WARNING RESET SWITCH By operating the tire pressure warning reset switch, the tire pressure warning ECU can be set to issue a warning at an inflation pressure that corresponds to the type of tires. Therefore, the dealer must set the warning threshold to the proper value in order to comply with local regulations. Operate the tire pressure warning reset switch only after the inflation pressures of all 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 ignition switch in the ON position. 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 at a frequency of once per minute. The initialization process is completed when signals from all tires have been received.

See also:
• INSPECTION - Step 1