TIRE PRESSURE MONITORING SYSTEM (TPMS)

id021200201000

Purpose

Caution

•  Each wheel unit has its own preset identification code. If a system component is replaced, the system becomes inoperative since the instrument cluster cannot recognize the identification codes. Therefore, be sure to configure the identification codes of wheel units when any of the following items have been performed. For the identification code configuration procedure, refer to the Workshop Manual.

―  Wheel unit replacement

―  Instrument cluster replacement

Note

•  Perform tire pressure adjustment before driving. (When tires are cold.)

•  Tire pressure changes due to changes in ambient temperature and internal tire temperature.

―  In an area or a season with varying of temperatures, tire pressure will change due to ambient temperature change. If the tire pressure is lower than the lower-limit pressure due to low ambient temperature, the TPMS warning light may illuminate. Adjust the pressure when the TPMS warning light illuminates.

―  Tire pressure rises after driving because the internal temperature of the tire is high, If tire pressure is adjusted to the standard value when the internal temperature of the tire is high, the tire pressure lowers when the internal temperature decreases to the same level as the ambient temperature. If the tire pressure is lower than the lower-limit temperature, the TPMS warning light may illuminate.

•  As a general reference, air pressure changes approx.10 kPa {0.1 kgf/cm², 1.5 psi} when the temperature changes 10 °C {18 °F}.

Function

―  Identification code recognition function

•  Recognizes whether received signals are from own wheel units.

―  Tire pressure determination/warning function

•  Compares received tire pressure data with preset values.

•  If the pressure is determined to be too low, the instrument cluster alerts the driver via the TPMS warning light and TPMS warning alarm.

Construction

Part name		Function
Wheel unit		•  Monitors air pressure, temperature, and acceleration of each tire, and sends RF signals. •  Sends data if any abnormality is detected in the wheel unit.
Keyless receiver		•  Send the RF signals received from the wheel unit to the start stop unit.
Start stop unit		•  Receives data from the keyless receiver. •  Sends data to the instrument cluster.
PCM	Vehicle speed signal	•  Inputs vehicle speed signals to the instrument cluster via CAN communication.
Instrument cluster		•  Receives data from start stop unit and monitor the air pressure of each wheel. If it determines from those signals that tire pressure is abnormal, it controls the TPMS warning light, flat tire warning light and TPMS warning alarm to alert the driver. ―  TPMS warning light •  If the instrument cluster detects abnormal air pressure or any abnormality in the system, the light is illuminated to alert the driver. ―  Flat tire warning light •  If the instrument cluster detects flat tire, the light is illuminated to alert the driver. ―  TPMS warning alarm •  If the instrument cluster detects abnormal air pressure or any abnormality in the system, the alarm is sounded to alert the driver. ―  Flat tire warning alarm •  If the instrument cluster detects flat tire, the alarm is sounded to alert the driver.

System structural view

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System wiring diagram

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Operation

•  The TPMS consists of wheel units that detect air pressure, temperature and acceleration of each tire, and an instrument cluster that receives data (RF signals) sent from the wheel units to monitor the air pressure of each tire.

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Identification Code Recognition Function

•  Since the identification codes of wheel units mounted on the vehicle have been configured in the instrument cluster, the instrument cluster can verify the identification codes sent from the wheel units against the configured identification codes.

•  When the received identification code agrees with the configured identification code, data such as tire pressure is updated according to the received signal. When the identification code does not agree, that signal data is ignored.

Tire Pressure Determination And Warning Function

•  The instrument cluster determines the tire pressure status of each wheel by comparing tire pressure data received from the wheel units with the preset values in the instrument cluster.

•  If a malfunction is detected in the received signals, the instrument cluster flashes the TPMS warning light to notify the driver of a tire malfunction.

•  The tire pressure monitoring function is classified into the two low-pressure and flat tire determinations.

•  The informing/warning of an abnormal tire pressure determination takes precedence over the informing/warning of a missing signal or malfunction determination.

Low-pressure determination

•  When tire pressure data is lower than the detection value configured in the instrument cluster, the instrument cluster determines that the tire for that wheel unit has low tire pressure.

―  If low tire pressure is determined when the ignition is on, the TPMS warning light is illuminated and sounds the TPMS warning alarm for 3 s to alert the driver.

―  If low tire pressure is determined when the ignition is off, the instrument cluster performs an open-circuit check^*1 on the TPMS warning light and flat tire warning light after the ignition is turned on, and then illuminates the TPMS warning light and flat tire warning light, and sounds the TPMS warning alarm and flat tire warning alarm for 3 s to alert the driver.

^*1: The instrument cluster turns on the TPMS warning light for 3 s after the ignition is turned on for an open-circuit check of the TPMS warning light.

•  The low-pressure determination is retained until tire pressure data from the applicable wheel unit returns to the preset value.

―  If tire pressure data that is higher than the specified value is received when the ignition is on, the instrument cluster turns out the TPMS warning light.

―  If tire pressure data that is higher than the specified value is received when the ignition is off, the instrument cluster performs an open-circuit check^*1 on the TPMS warning light after the ignition is turned on and turns out the TPMS warning light.

^*1: The instrument cluster turns on the TPMS warning light for 3 s after the ignition is turned on for an open-circuit check of the TPMS warning light.

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Flat tire determination

•  The instrument cluster determines that there is a flat tire when it receives a signal that the air pressure is lower than the specified low-pressure value, and then it illuminates the flat tire warning light and sounds the flat tire warning alarm.

―  The flat tire warning light turns off when the system detects that the flat tire has been repaired.

―  When a flat tire is detected, the flat tire warning alarm sounds every time the ignition is turned on until recovery is detected.

―  The system stores the most recent data when the power is cut (battery removal/installation) and holds this data until the ignition is turned on next time.

―  The system stores puncture and recovery freeze frame data.

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