Tire Pressure Warning System - Diagnostics: Overview Lexus GX J120

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1. TIRE PRESSURE WARNING SYSTEM PRECAUTION When the tire pressure warning lamp comes on, immediately check the tire pressure and adjust it to the specified value. (The tire pressure warning lamp comes on if there is an open in the tire pressure warning lamp circuit.) NOTE: Check the spare tire as well since this system monitors pressure of all tires. TIRE PRESSURE SPECIFICATIONS Front Rear Spare 220 kPa (2.2 kgf/cm 2 , 32 psi) 220 kPa (2.2 kgf/cm 2 , 32 psi) 220 kPa (2.2 kgf/cm 2, , 32 psi) When the tire pressure warning lamp blinks, there is a malfunction in the system. Check for DTCs. Changing the tire pressure warning switch between "MAIN" and "2nd" allows registration of 2 transmitter ID sets. Check the tire pressure warning switch to see whether the tire is registered in "MAIN" or "2nd". If the vehicle is driven without selecting switch state correctly, the tire pressure monitor ECU determines the system is malfunctioning and causes the tire pressure warning lamp to blink. It is necessary to register the transmitter ID in the tire pressure monitor ECU when replacing the tire pressure monitor valve sub-assy and/or tire pressure monitor ECU (see «REGISTRATION»(ref-228752-S10556775882006041100000) ). When replacing the tire pressure monitor ECU: Using the DATA LIST, read the transmitter IDs registered in the ECU and make a record of them before removing the tire pressure monitor ECU. Register the transmitter IDs after installing a new tire pressure monitor ECU. When replacing the tire pressure monitor valve sub-assy: Make a record of the 7 digit number (transmitter ID) written on the tire pressure monitor valve sub-assy when replacing the tire pressure monitor valve sub-assy. Register the transmitter IDs in the tire pressure monitor ECU after replacing the tire pressure monitor valve sub-assy and installing the tires and wheels on the vehicle. NOTE: The transmitter ID is written on the tire pressure monitor valve sub-assy and ID can not be seen after installing the tire pressure monitor valve sub-assy on the tire and wheel. Therefore, make a record of the transmitter ID before installing the tire pressure monitor valve sub-assy.
2. IN CASE OF TIRE AND WHEEL REPLACEMENT When tires and wheels are replaced, always register the transmitter ID.
3. FAIL-SAFE FUNCTION If there is a malfunction in the tire pressure monitor ECU, the ECU blinks the tire pressure warning lamp and prohibits operating the tire pressure warning system. The result of this diagnosis is stored in the tire pressure monitor ECU.

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SYSTEM DESCRIPTION

1. DESCRIPTION OF SYSTEM A tire pressure monitor valve sub-assy equipped with tire pressure sensor, transmitter is installed in a tire wheel assy. The sensor measures the tire pressure and the measured value and transmitter ID are transmitted to the tire pressure monitor receiver assy on the body as radio waves and then sent to the tire pressure monitor ECU from the tire pressure monitor receiver. If the transmitter ID has already been registered, the ECU compares the measured tire pressure value and the warning threshold pressure value. When the value is less than the warning threshold pressure value registered in the tire pressure monitor ECU, the tire pressure warning lamp on the combination meter comes on.
2. WHEN TIRE PRESSURE WARNING LAMP IS LIT When the tire pressure warning lamp does not go off, or when it comes on during driving, check tire pressure. If the tire pressure warning lamp comes on within several hours after adjusting the tire pressure, the tire may have a slow air leak. If the tire pressure warning lamp comes on even after adjusting the tire pressure, selection of the tire pressure warning switch "MAIN" / "2nd" may be incorrect. Under the following conditions, the system may not function properly. The areas, facilities or devices that use similar radio wave frequencies are located in the vicinity of the vehicle. A radio device of similar frequency is used near the vehicle. A lot of snow or ice is stuck to the vehicle, especially the wheels and around the wheel houses. The battery of the sensor has been depleted. The tires without tire pressure monitor valve sub-assy are used. Tire chains are used. Wheels other than manufacturer spec LEXUS GX 470 wheels are used. Although the tires with tire pressure sensors are used, another tire set has been selected by the tire pressure warning switch. HINT: If any other wheels than the specified ones are used, the system may not function properly because the radio waves are differently transmitted from the tire pressure sensor. Depending on the tire type, the system may not function properly even though the specified wheels are used. The average life of the grommet of the tire pressure monitor valve sub-assy is approximately 5 years, at which time it must be replaced. Re-tighten the valve nut if the valve is air leaking, is less than 5 years old and there is no problem with grommets. Torque: 4 N.m (41 kgf.cm, 36 in.lbf) After removing and installing the ECU or a sensor, output a diagnosis code and check that it is a normal system code.
3. FUNCTION OF COMPONENTS COMPONENTS FUNCTION Components Function Tire pressure monitor valve sub-assy Combined as a single unit with a disc wheel air valve, it measures tire pressure and temperature and transmits an ID number for measurement value and identification. Built-in the battery. Tire pressure monitor receiver assy Receives and transmits a necessary signal from the transmitter to the tire pressure monitor ECU. Tire pressure monitor ECU Receives the signal from the receiver and identifies it as vehicle's own signal. If the measurement value is equal to or lower than the specified value, it transmits a signal so that the air pressure warning lamp on the combination meter comes on. Tire pressure warning switch When 2 sets of IDs are registered in the tire pressure monitor ECU, either of the sets can be selected by changing the switch between "MAIN" and "2nd". Tire warning lamp Located in the instrument panel, it informs the driver of lowered tire air pressure and system failure.