Tire Monitor System - Diagnostic Tips
PRODUCT GENERAL INFORMATIONPG001-07
Title:
DIRECT-TYPE TIRE PRESSURE
WARNING SYSTEM DIAGNOSTIC TIPS
Models
'04 - '08 Applicable Lexus
March 20, 2007
Introduction
The Tire Pressure Warning System (TPWS) monitors the difference in tire pressure in all four or five tires (if the vehicle is equipped with a full-size spare tire) through radio wave signals from a tire pressure valve/sensor mounted in each wheel.
This bulletin provides system overview and diagnostic information for the direct-type TPWS.
Applicable Vehicles
^ 2004 - 2007 model year GX 470 vehicles.
^ 2006 model year GS 300 vehicles.
^ 2006 - 2007 model year GS 430, IS 250/350, and LX 470 vehicles.
^ 2007 model year ES 350, GS 350, LS 460, RX 350, and SC 430 vehicles.
^ 2008 model year RX 350 vehicles.
Required Tools & Equipment
Warranty Information
Summary of TPWS/Component Operation
The illustration is an example of the TPWS component locations on 2007 model year RX 350 vehicles:
For exact location of each vehicle's TPWS components, refer to the Technical Information System (TIS), applicable model and model year Repair Manual, Suspension - Tire Pressure Monitoring System (see component or parts location). For additional information on the TPWS components and operation, refer to TIS, applicable model and model year New Car Features.
Tire Pressure Warning Valve/Sensor:
Each wheel (including the spare tire on certain vehicles) has a tire pressure warning valve/sensor integrated into the air valve with a unique ID number that measures the tire pressure and tire temperature and then transmits the information to the antenna/receiver mounted inside the vehicle through a radio wave signal. The unique ID number must be manually entered into the ECU using TIS Techstream whenever the tire pressure warning valve/sensor is replaced or after a tire and wheel are exchanged.
Vehicles equipped with a tire pressure warning valve/sensor inside the spare tire are listed in the table shown.
Tire Pressure Warning System Antenna/Receiver:
The antenna/receiver receives each tire pressure, tire temperature, and the unique tire pressure warning valve/sensor ID numbers through radio wave signals from the tire pressure warning valve/sensors and then transmits the information to the TPWS ECU.
Tire Pressure Warning System ECU:
The ECU takes each tire pressure, tire temperature, and unique tire pressure warning valve/sensor ID information from the antenna/receiver and compares it to the specified value, which was registered during PDS. If the information received does NOT match the specified value registered in the ECU, it will transmit a signal to illuminate the Tire Pressure Warning System Indicator Light located on the combination meter. If the ECU is replaced, it is necessary to manually enter the tire pressure valve/sensor ID numbers using TIS Techstream.
Tire Pressure Warning System Indicator Light:
The Tire Pressure Warning System
Indicator Light on the combination meter is illuminated or flashes continuously when the ECU senses that the tire pressure, tire temperature, and/or unique ID number does NOT match the specified value registered in the ECU.
Conditions for the Tire Pressure Warning System Indicator Light "ON" or "Flashing" are listed in the table shown.
Initialization/"SET" Switch:
When initializing the TPWS, the present tire pressure is set as the standard pressure (for example: 32 psi). The TPWS determines a decrease in air pressure by comparing the standard pressure to the tire inflation pressure received from the tire pressure warning valve/sensor.
Reasons for initializing the system include:
^ When rotating tires that have different tire pressures in the front and rear.
^ When changing or adjusting the tire pressure.
^ When changing tire size or when tires are replaced.
"MAIN/2nd" Switch:
The "MAIN/2nd" switch allows the owner to have two different sets of tires and wheels, with two different sets of tire pressure warning valve/sensor ID numbers. For example, the second set would be used for snow tires. Register both the main and the second set of tire pressure warning valve/sensor ID numbers in the TPWS ECU using TIS Techstream. Depending on what set of tire pressure warning valve/sensor ID numbers are being registered, the "MAIN/2nd" switch must be set in the correct position (i.e., "MAIN" for regular use tires and "2nd" for snow use tires).
^ "MAIN/2nd" switch in the UP position The TPWS ECU is programmed to read the main set of tire pressure warning valve/sensor ID numbers.
^ "MAIN/2nd" switch in the DOWN position The TPWS ECU is programmed to read the second set of tire pressure warning valve/sensor ID numbers.
TIS Techstream Setup
When diagnosing the TPWS with TIS Techstream, it must be set up to read the tire pressures in psi - gauge" (psi - g). Follow the screens below from TIS Techstream to convert the tire pressures to psi - g.
1. Click Setup > User Preferences > Unit Selection.
2. On the Unit Selection dialog box, verify Air Pressure is set to gauge and psi (see the area outlined in red in the following screenshot).
System Concerns & Repair Methods
Registration Procedure
TIS Techstream Registration of Tire Pressure Warning Valve/sensor ID Numbers:
1. Click Connect to Vehicle (refer to "1" in the following screenshot).
2. Adjust vehicle information as necessary (refer to "2" and the area outlined in red in the following screenshot).
3. Click Next (refer to "3" in the following screenshot).
4. Select Tire Pressure Monitor (A) > Utility (B) > ID Registration (C) (refer to the following screenshots).
5. Follow the onscreen utility instructions (refer to the following screen shots).
Diagnostic Flow Chart