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Tire Pressure Monitor Description and Operation

Tire Pressure Monitor Description and Operation


The following systems are involved in the Tire Pressure Monitoring System.


• BCM

• RFA

• TPMS

• ALM (not US/CA/CN)

• IPC

• DIC


System Description

The tire pressure monitor sensor, one in each wheel assembly, sends sensor ID, tire temperature, tire pressure and tire rotation direction via radio frequency communication (RF).

The Remote Function Actuator (RFA) receives and translates the data contained in each sensor's RF transmission and sends sensor ID, tire pressure and temperature data via the serial data communication link to BCM.

ALM reads the RF from the sensors. By using the values for sensor ID and tire rotation direction together with measuring the field strength from the sensors ALM can find out which sensor ID belongs to which tire. The corner positions are sent via the serial data link (LIN bus 2) to BCM. (Not US/CA/CN)

BCM holds the TPM application, calculates whether the tire pressure is OK or not, sets fault codes and sends data messages to DIC and IPC via serial communication data link requesting the appropriate tire pressure monitor indicator illumination and also to display the appropriate data message.

Auto Learn Module (ALM) (Not US/CA/CN)

ALM reads the RF from the sensors. By using the values for sensor ID and tire rotation direction together with measuring the field strength from the sensors ALM can find out which sensor ID belongs to which tire. The corner positions are sent via the serial data link (LIN bus 2) to BCM.

ALM re-checks the configuration after each start when the speed is more than 20 km/h (15 mph). If one or more sensors has been replaced or if the tires were shifted on the car, it can take up to 10 minutes of driving (accumulated time) before placement is "learned". If no changes have been made, it only takes a few minutes. Refer to Tire Pressure Indicator Sensor Learn .

Manual Learn Mode Description (Only US/CA/CN)

Note

When enabling the learn mode the gear lever for automatic transmission must be in park position. With manual transmission the park brake lever/switch must be in park position, i.e. hand-brake need to be pulled.


The tire pressure monitor (TPM) system uses 4 Tire Pressure Monitor Sensors, Remote Function Actuator (RFA), Body Control Module (BCM), Driver Information Center (DIC), Instrument Panel Cluster (IPC), and serial data communication circuits to perform the TPM learn mode functions.

The sensors learn procedure must be performed after every wheel rotation, BCM replacement, or sensor replacement. Once the learn mode has been enabled, each of the sensors unique identification codes can be learned into the BCM memory. The BCM must learn the sensor IDs in the proper sequence to determine correct sensor location. The first learned ID is assigned to the left front location, the second to right front, the third to right rear and the fourth to left rear. The turn signals will individually illuminate indicating which location is to be learned in the proper sequence. When a sensor ID"s have been learned to the BCM the horn chirps two times, which indicate learn complete.

Tire Pressure Monitor Sensor

The tire pressure monitor sensor, one in each wheel assembly, sends sensor ID, tire temperature, tire pressure, via radio frequency communication (RF). There is no tire pressure monitor sensor in the spare wheel, if equipped. Each tire sensor has an internal battery power supply which last 160 000km (100 000miles) or 10 year service life whichever come first.

When the vehicle is stationary, the sensors internal accelerometer is inactive, which puts the sensors into a stationary state. In this state the sensors sample tire pressure once every 30 seconds and do not transmit at all if the tire pressure does not change. As vehicle speed increases to above 20 km/h (15 mph), centrifugal force activates the sensors internal accelerometer causing the sensors to go into rolling mode. In this mode, the sensors sample tire pressure and temperature once every 10 seconds and transmit in rolling mode once every 60 seconds.

Immediately after transitioning from rolling into stationary mode, the sensors do not transmit any longer.

The sensors continuously compare their last pressure transmission to their current pressure sample and will transmit in re-measure mode if an 8.3 kPa (1.2 psi) change in tire pressure has been detected in either a stationary or rolling state

Remote Function Actuator (RFA)

RFA receives and translates the data contained in each sensor's RF transmission and sends sensor ID, tire pressure and temperature data via the serial data communication link to BCM. For more information on other functions of the RFA. Refer to Keyless Entry System Description and Operation (With ATH) Keyless Entry System Description and Operation (Without ATH) .

Body Control Module (BCM)

BCM holds the TPM application, calculates whether the tire pressure is OK or not, sets fault codes and sends data to DIC and IPC via serial data link.

BCM keeps sensor IDs and their location even after battery disconnect. If a tire pressure is below the tire low value a message is sent via the serial data communication link to DIC and IPC.

Is the value only below the comfort threshold value, a message is sent only to DIC (Not US/CA/CN) .

To reset a warning fill the tires to placard value or more (see the sticker at the left B pillar).

Note

Tire pressure date refers to cold tires and applies both to summer and winter tires.


TPMS checks the tires pressure with the reference from the placard values. TPMS checks whether the temperature compensated tire pressures has dropped below any of the threshold values specified for comfort warning or low pressure warning. TPMS also check the tire pressure differences on the same axel (Tire Pressure Imbalance). If tire pressure is increased to a value suitable for high-load or high speed driving TPMS recognizes this and increases the threshold values per axle, i.e. adaptive threshold.

TPMS checks the tires pressure threshold low warning with the reference from the placard values (Only US/CA/CN) .

Instrument Panel Cluster (IPC)

IPC has the tell-tale for TPM. The bulb will be checked at ignition on in the normal IPC bulb check.

In case of under-inflation below the threshold level for one or more tires the tire pressure monitor indicator tell-tale will be illuminated after the ignition is turned ON. The indicator can be extinguished by adjusting tire pressure to the recommended values. Refer to Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label . Then drive the car over 20 km/h (15 mph) for up to 10 minutes.

In case of a system failure the tire pressure monitor indicator tell-tale will be activated after the ignition is turned ON, or if the malfunction occurs during driving. It will flash for 60-90 seconds and then remain illuminated.

The tire pressure monitor indicator tell-tale will not be illuminated for comfort or when Winter Mode is detected.

Driver information center

The BCM sends the raw tire pressure values and corner location data via the serial data link to the DIC where they are displayed.

The DIC will display "--" instead of tire pressure


• If the battery has been disconnected and until RFA has received new data

• If TPM is in Winter Mode (Not US/CA/CN)


If data is missing for one or more tire pressure sensors "--" will be displayed for that particular wheel if DTC for Tire Pressure Sensor Fault is set.

DIC also shows text messages for


• Too low tire pressure per corner

• Any malfunction detected

• Imbalanced tire pressure per axle (Not US/CA/CN)

• Winter mode (Not US/CA/CN)


The DIC tire pressure message can be extinguished by adjusting tire pressure to the recommended values. Refer to Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label . Then drive the car over 20 km/h (15 mph) for up to 10 minutes (accumulated driving).