Service

TPMS: Lexus RX Series, 2016-19

Information provided by Mitchell 1
Posted on August 15, 2019
Figure 1: Identifying the TPMS steering wheel controls. All artwork courtesy of Toyota, License Aagreement TMS 1002.
Figure 1: Identifying the TPMS steering wheel controls. All artwork courtesy of Toyota, License Aagreement TMS 1002.

SUBJECT VEHICLES: Lexus RX 350 (2016-19), RX 350L (2019), RX 450h (2016-19) and RX 450hL (2019).

SPECIAL TOOLS NEEDED? Yes, a Toyota Techstream.

NOTE: The tire pressure monitoring system (TPMS) will need to be initialized when tires are rotated; tires are replaced with tires of different pressures; tire pressure sensor and/or tire pressure monitor engine control unit (ECU) are replaced. Set tire pressure within the specified range before initializing. When a tire pressure sensor and/or tire pressure monitor ECU are replaced, the sensor ID must be memorized by the tire pressure monitor ECU prior to system initialization. See “Reset procedures.”

NOTE: Initialization is NOT required if re-inflating tires to the specified tire pressure.

In Lexus RX Series vehicles (2016-2019), a tire pressure warning valve and transmitter (equipped with a tire pressure sensor and a transmitter) is installed in each tire and wheel assembly. The sensor measures the tire pressure, and the measured value and transmitter ID are transmitted to the tire pressure monitor antenna on the body as radio waves. These radio waves are 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 air pressure value with the standard value. When the value is less than the standard value registered in the tire pressure monitor ECU, the warning light on the instrument cluster comes on and a warning message will be shown on the multi-information display.

CAUTION: The warning system may not activate immediately if bursts or sudden air leakage should occur. The tire pressure warning reset switch is used to address the differences in the air pressure settings by the type of tires, or the differences in pressure between the front and rear tires. This switch is used to initialize the warning system after certain repair procedures.

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 in or 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.
  • A tire without a tire pressure warning valve and transmitter is used.
  • Tire chains and/or the spare tire are used.

If other wheels than the specified ones are used, the system may not function properly because the radio waves are differently transmitted from the sensor. Depending on the tire type, the system may not function properly even though the specified wheels are used.

Tire pressure monitor warning indicators

NOTE: The tire pressure warning light may turn on due to natural causes such as natural air leaks or tire pressure changes caused by temperature. In this case, adjusting the tire pressure will turn off the warning light.

When the tire pressure warning light and message do not go off, or when they come on during driving, check tire pressure and adjust as necessary. Warning indicators should turn off a few minutes after air is put into a deflated tire. If the warning indicators are still on even though the tire pressure is correctly adjusted, the tire could be punctured. Repair as necessary. If the tire pressure warning indicators come on within several hours after adjusting the tire pressure, the tire may have a slow air leak. If the warning light is still on or blinking, there is a malfunction in the TPMS. See appropriate manufacturer service information.

Reset procedures

NOTE: The system will need to be initialized when tires are rotated; tires are replaced with tires of different pressures; tire pressure sensor and/or tire pressure monitor ECU are replaced; or when a new vehicle is delivered. Set tire pressure within the specified range before initializing. See “Initializing tire pressure monitor system.” When a tire pressure sensor and/or tire pressure monitor

ECU are replaced, the sensor ID must be memorized by the tire pressure monitor ECU prior to system initialization. See “Tire pressure sensor registration.” TPMS reset is not required if re-inflating tires to the specified pressure. Warning indicators should turn off a few minutes after air is put into a deflated tire.

Initializing the TPMS

NOTE: When initializing the system, the present tire condition is stored as a standard.

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 monitor ECU at a frequency of one per minute. The initialization process is completed when the signals from the tires (including the spare tire) have been received.

1) Set the tire pressure of all the wheels to the pressure specified on the tire and loading information label.

2) With the vehicle stopped and parking brake applied, turn the engine switch on (IG).

3) Use the Lft/Rht ARROW buttons on the right-hand steering wheel control pad (see Figure 1) and select the GEAR icon.

4) Use the Up/Dwn ARROW buttons and select VEHICLE SETTINGS. Then press ENTER (center button).

NOTE: “- -” will be displayed for inflation pressure of each tire on the multi-information display while the tire pressure warning system determines the position of each tire. When the position of each tire is determined, the inflation pressure of each tire will be displayed on the multi-information display.

5) Use the Up/Dwn ARROW buttons and select TPMS. Then press and hold ENTER until the tire pressure warning light will blink slowly 3 times.

6) Drive the vehicle at approximately 25 mph (40 km/h) or more for approximately 10 to 30 minutes until the inflation pressure of each tire is displayed on the multi-information display.pressure sensor registration.

Figure 2: Locating the tire pressure warning valve transmitter ID.
Figure 2: Locating the tire pressure warning valve transmitter ID.
NOTE: If the tire pressure sensor and/or tire pressure monitor ECU are replaced, the transmitter ID needs to be registered in the tire pressure monitor ECU prior to system initialization. To perform this procedure, the Toyota Techstream must be used. It is not necessary to register the sensor IDs when only tire rotation is performed. NOTE: Take note of the 7-digit number (transmitter ID) written on the tire pressure warning valve and transmitter (see Figure 2).

1) Set the tire pressure of all wheels to pressure specified on the tire and loading information label.

2) Connect the Techstream to DLC3.

3) Turn the engine switch on (IG).

4) Enter the following menus: Chassis / Tire Pressure Monitor / Utility / ID Registration.

NOTE: If the system is in the initialization mode, it is unable to perform registration. Therefore, restart the registration after terminating the initialization or confirming that the initialization has been completed.

5) Perform the procedures displayed on the Techstream.

6) Confirm the transmitter ID registration by entering the following menus: Chassis / Tire Pressure Monitor / Data List.

7) Read the “ID Tire Inflation Pressure” values.

8) Confirm that the tire pressure data of all tires (including the spare tire) is displayed on the Techstream screen.

9) Disconnect the Techstream with the ignition switch off.

Demounting/mounting procedures

CAUTION: The tire should be demounted from the wheel using the tire changer manufacturer’s instructions. Use the following information to avoid damage during the demounting/mounting procedures.

NOTE: The system will need to be initialized when tires are rotated; tires are replaced with tires of different pressures; tire pressure sensor and/or tire pressure monitor ECU are replaced. Set tire pressure within the specified range before initializing. When a tire pressure sensor and/or tire pressure monitor ECU is replaced, the sensor ID must be memorized by the tire pressure monitor ECU prior to system initialization. See “Reset procedures.”

Tire pressure sensor

CAUTION: DO NOT try to install a tire pressure sensor in a steel wheel or aftermarket wheel. Use only in original style factory wheels. CAUTION: The use of tire sealants is strictly prohibited for vehicles equipped with a TPMS. Tire sealants can clog tire pressure sensors.

NOTE: The average life of the grommet of the tire pressure warning valve and transmitter is approximately 5 years, at which time it must be replaced. If the valve is leaking air, is less than 5 years old and there is no problem with grommets, retighten the valve nut to 35 in.-lbs. (4 N.m). Whenever the tires must be replaced, replace the grommets for the tire pressure sensors as well.

NOTE: If the tire pressure warning valve and transmitter is going to be replaced, make a note of the 7-digit number (transmitter ID) before installation, as it cannot be seen after sensor is installed (see Figure 2). Whenever a new sensor is installed, it will need to be registered in the tire pressure monitor ECU.

Figure 3: Exploded view of the tire pressure warning valve and transmitter.
Figure 3: Exploded view of the tire pressure warning valve and transmitter.
Removal

1) When replacing a wheel or tire, the tire pressure sensors must be set up in one of the following ways:

  • Remove the sensor from the old wheel and install it to the new wheel. Keep the same wheel with the tire pressure sensor, and replace only the tire.
  • Use a new wheel and sensor (the new sensor must be registered after installation).

2) Remove the wheel. Remove the valve core and cap, and release air from the tire (see Figure 3) . NOTE: Keep the removed cap and valve core.

3) After ensuring that air is sufficiently released, remove the nut and washer that is used to secure the tire pressure warning valve and transmitter and drop the sensor inside the tire. NOTE: Be careful not to damage the tire pressure warning valve and transmitter due to interference between the sensor and tire bead.

Figure 4: Disengaging the bead using a tire remover.
Figure 4: Disengaging the bead using a tire remover.
4) After dropping the tire pressure warning valve and transmitter into the tire, disengage the bead using the shoe of the tire remover (see Figure. 4).

5) Remove the bead on the upper side in the usual operation.

6) Remove the tire pressure warning valve and transmitter from the tire, and remove the bead on the lower side as in usual operation. NOTE: The tire pressure warning valve and transmitter is powered by a lithium battery. When disposing, remove the battery and dispose of it properly.

7) Remove and discard the inner grommet from the tire pressure warning valve and transmitter.

Installation

1) Insert the tire pressure warning valve and transmitter into the valve installation hole. Insert from the inside of the rim so that the print surface can be seen (see Figure 2).

Check for the following:

  • Check that there is no visible deformation, damage or other abnormalities on the transmitter and that there is no foreign matter on the inner grommet and around the rim hole.
  • If installed in the reverse direction, the tire pressure warning valve and transmitter may be damaged or fail to transmit signals when running at high speed.
  • If installing a new tire pressure warning valve and transmitter, write down the ID number before installation (see Figure 2). It is necessary to register an ID in the ECU after installation.
    Figure 5: Installing a tire pressure warning valve and transmitter.
    Figure 5: Installing a tire pressure warning valve and transmitter.

2) Install the washer on the valve and transmitter from the rim side, and tighten the nut to 35 in.-lbs. (4 N.m) (see Figure 5). Check for the following:

  • Ensure there is no foreign matter on the washer and nut. If the tire pressure warning valve and transmitter was removed, check that there is no damage or cuts, and no foreign matter such as mud, dirt or sand attached to the grommet. Replace the grommet with a new one. Check that there is no oil, water or lubricant around the rim hole, tire pressure warning valve and transmitter, washer and nut. Failing to do so may result in improper installation.

3) After the tire is inflated, the valve nut may be loose. Retighten the nut to the specified torque, and then check for air leaks with soapy water. CAUTION: If the sensor is positioned outside this area, it generates interference with the tire bead, causing possible damage to the sensor.

4) Set the wheel disc to the mounting machine, and install the lower tire bead. Position the main body of the sensor in the shaded area as shown in the illustration (see Figure 6).

Figure 6: Positioning the tire pressure warning valve and transmitter.
Figure 6: Positioning the tire pressure warning valve and transmitter.
5) Making sure that the tire bead and tool do not interfere with the main body of the sensor and that the sensor is not clamped by the bead, install the upper bead.

6) When putting air into the tire, first install the tire pressure valve straight on the stem of the tire pressure warning valve and transmitter.

7) Install tire and wheel assembly.

8) When a new sensor is installed, the ID code will need to be registered.

See “Reset procedures.” ■

Information for this column comes from the tire pressure monitoring systems data in ProDemand®, Mitchell 1’s auto repair information software for domestic and import vehicles. Headquartered in Poway, Calif., Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918. For more information, visit www.mitchell1.com.

Related Topics: Mitchell 1, service, tire pressure monitoring system, TPMS

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