# Tire Pressure Monitoring System

## Overview

### Component Location

### General

WARNING: The TPMS is not a substitute for manually checking tire pressures and cannot register damage to a tire. The TPMS only provides a tire pressure warning and does not re-inflate the tires.
WARNING: Do not use any tire liquid or aerosol tire sealant other than the one supplied with the vehicle, as this might cause a malfunction of the tire pressure sensors.

The Tire Pressure Monitoring System (TPMS) monitors the air pressure and temperature of each tire and transmits this information via a Radio Frequency (RF) signal to the antenna module.

If the air pressure in one or more tires is above or below a prescribed value, a message is sent to the instrument panel and the TPMS indicator light displays.

NOTE: If the TPMS light is displayed shortly after a tire has been replaced or repaired using a different tire sealant than the one supplied with the vehicle, the TPMS wheel sensor might have been damaged.

If a drop in tire pressure is detected, or if there is a fault with the system, the amber Tire Pressure Monitoring System (TPMS) indicator light displays on the instrument panel. The indicator light only advises that the pressure is low on one or more tires. No actual pressures are displayed and it is the user’s responsibility to determine which tire(s) require attention.

WARNING: It is the driver’s responsibility to maintain correct tire pressure, even if under-inflation has not reached the level to trigger the TPMS warning light.
CAUTION: Driving on a significantly under-inflated tire causes the tire to overheat and can lead to sudden tire failure. Under-inflation also reduces fuel efficiency and tire tread life and may affect the vehicle’s handling and braking ability.

## Component Descriptions

### TPMS Wheel Sensors

1. Valve stem retaining screw

2. Sensor unit

3. O-ring

4. Valve stem

5. Valve nut

The sensor is secured to the valve stem by a retaining screw. The sensor fits through the valve hole in the wheel rim, and is secured with the valve nut. It is sealed with an O-ring. The curvature of the sensor follows the form of the wheel rim.

The wheel sensor contains a filter which prevents contamination by water vapor or dirt. The sensor also contains a pressure sensor, a signal processor, and an RF antenna. An integral temperature sensor prevents pressure readings from being affected by variations in temperature. Each sensor has a lithium-ion battery that has a life of up to 10 years.

The wheel sensors have a pressure measurement range of 7.25 psi to 92.5 psi (0.5 bar to 6.3 bar) and a temperature operating range of -40°F to +248°F (-40°C to +120°C).

When a new sensor is installed, it must learn its position in the system before the TPMS can operate correctly. For more information, see Sensor ID Learn Procedure.

### TPMS ECU

1. ECU

The TPMS electronic control unit (ECU) is installed at the rear of the vehicle above the rear diffuser. It contains a 433 MHz RF receiver, a data de-modulator, a data decoder, and an antenna.

## Operation

### TPMS Operation

1. TPMS indicator

When the acceleration sensor within the wheel sensor detects centrifugal force equivalent to 25 mph, the sensor begins transmitting pressure and temperature data every 4 seconds. When the sensor is stationary, it transmits every 40 seconds. If pressure changes rapidly, either falling or rising, the sensor transmits every 4 seconds, even when stationary. The wheel sensor transmits pressure and temperature data over a wireless Radio Frequency (RF) link to the antenna module. Error protection of the transmitted signal is provided by a cyclic redundancy check algorithm.

The antenna module receives the data and converts it to a CAN message, which is then broadcast on the chassis bus. The vehicle firmware determines when to turn on the TPMS indicator light.

The TPMS indicator light does not immediately turn off when the tire pressure is adjusted. After the tire is inflated to the recommended pressure, the vehicle can either be left stationary in drive mode or driven at speeds above 25 mph (40 km/h). It should not take more than 3 minutes while stationary or 1 minute while driving to activate the TPMS and turn off the indicator light.

### TPMS Malfunctions

The TPMS indicator light also displays when the system is not operating correctly.

The TPMS malfunction indicator light is combined with the tire pressure indicator. When the system detects a malfunction, the indicator light flashes for approximately one minute after the vehicle is turned on and then displays continuously. This sequence repeats for subsequent vehicle start-ups as long as the malfunction exists. The system might not be able to detect or signal low tire pressure as intended.

TPMS malfunctions can occur for a variety of reasons, including the installation of replacement or alternate tires or wheels on the vehicle that prevent the TPMS from functioning properly.

Any time the TPMS sensors are not reinstalled in the same locations (for example, when rotating the tires), perform the TPMS sensor ID learn procedure.

### Sensor ID Learn Procedure

The TPMS sensor learn procedure requires the use of the TPMS SmarTool.

1. TPMS SmarTool

2. Cable connector

3. Diagnostic cable, part No. 1013758-01-A

Refer to Service Manual procedure 34015100 to perform the TPMS sensor ID learn procedure.

#### Setting Pressure Thresholds

TPMS thresholds vary depending on suspension type, tire size, and region. In the Service Manual, refer to General Information > Technical Data > Tire pressures for a current list of thresholds.

Setting the pressure thresholds requires the TPMS SmarTool. Refer to Service Manual procedure 34015500 to set the TPMS thresholds.

#### Interference

When many vehicles are together in the service area, TPMS sensors might interfere with each other and cause a TPMS fault to occur. The SmarTool might be slow to respond or work incorrectly in this environment. Moving the vehicle further away from other vehicles during programming improves reliability.