Tire pressure monitor function - GF40.15-P-0001TR

MODEL 211 as of 1.6.05 with CODE (475) Tire pressure monitor II except CODE (494) USA version except CODE (498) Japan version

MODEL 211 as of 1.7.05 with CODE (475) Tire pressure monitor II except CODE (494) USA version except CODE (498) Japan version

Location of components

Fig 1: Locating Tire Pressure Monitor Components

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Networking of components

Fig 2: Tire Pressure Monitor Communication Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

General

The TPM system serves the purpose of permanently monitoring the tire inflation pressure.

For this purpose, tire inflation pressure and tire temperature are measured in the tire at certain intervals and transmitted by telemetrics to the TPM [RDK] control unit via a HF transmission path.

The TPM system assists the driver with monitoring the correct tire inflation pressure and thus serves the purpose of active safety.

Via the multifunction display (A1p13) in the instrument cluster the driver is informed about the current tire inflation pressure or about the necessary corrections to the tire inflation pressure and about flat tires.

Preventative safety is increased by the TPM system:

Tire bursts due to excessive flexing energy and driving quickly with too low air pressure are avoided.
The driver is requested to check the tire inflation pressure.
A timely warning ensues in the event of a rapid pressure drop (pressure drop greater than 0.2 bar/minute).
Regular checking of tire inflation pressure is simplified.

The nature of the system is such that a sudden pressure drop cannot be detected.

Service life and economy

Tire wear and fuel consumption are reduced by having the correct tire pressure.

The TPM system does not relieve the driver of the duty to make a regular manual check of the tire inflation pressure (at least every 14 days). In the process the correct tire inflation pressure must be adjusted by means of the table in the fuel filler flap. The TPM system does not warn against an incorrectly adjusted tire inflation pressure.

The TPM system consists of the following components:

Left front TPM [RDK] wheel antenna
Right front TPM [RDK] wheel antenna
Central TPM [RDK] antenna
Left front TPM [RDK] wheel sensor
Right front TPM [RDK] wheel sensor
Left rear TPM [RDK] wheel sensor
Right rear TPM [RDK] wheel sensor
TPM [RDK] control unit
Scroll forward/back button
Buttons + and - for setting specific functions and volume control

Function

The wheel sensors are attached to the metal valves on the rims, are not visible from outside, and measure the air pressure in the tires and the tire temperatures.

While driving information is transmitted by radio signal on the absolute pressure in the tires, the acceleration, the temperature on the front left, front right, rear left and rear right TPM wheel sensors, as well as an ID (individual serial number) for identifying the tire.

The ID serves the purpose of detecting the wheels fitted to the vehicle and not of ascertaining the location (e.g. left front).

The signals are received by the central TPM [RDK] antenna and are relayed to the TPM [RDK] control unit via a discrete cable. The left front TPM [RDK] wheel antenna and the right front TPM [RDK] wheel antenna produce trigger signals for ascertaining the location of the front wheels.

This allows wheel-specific pressures to be displayed. The location of the rear wheels is detected when cornering by means of the turn angle and the different rear wheel speeds.

While driving the left front, right front, left rear and right rear TPM [RDK] wheel sensors transmit three data telegrams every 60 seconds. These data telegrams transmit the absolute pressure, the wheel temperature, the acceleration, the ID and status information on the manufacturer, frequency, pressure range etc. The tire pressuring measuring range extends from 0 to 5.5 bar (relative pressure).

The TPM [RDK] control unit is permanently operational. Each time the CAN-B (Controller Area Network bus class B (interior)) is alerted by a vehicle start or ignition "ON", the TPM [RDK] control unit performs a reinitialization and starts to transmit messages to the instrument cluster.

In the TPM [RDK] control unit the air pressure, set and activated by the driver, of each wheel is stored as the specified pressure to be monitored.

The data evaluated by the TPM [RDK] control unit is displayed in the multifunction display of the instrument cluster in the form of messages relevant to function and operation.

Tire pressure monitor (TPM), activation	GF40.15-P-0001-02TR
Displaying tire inflation pressure with tire pressure monitor (TPM)	GF40.15-P-0001-03TR
Tire pressure monitor (TPM), messages relevant to function	GF40.15-P-0001-04TR
Tire pressure monitor (TPM), messages relevant to operation	GF40.15-P-0001-05TR
Tire pressure monitor control unit, component description	GF40.15-P-5124TR
Wheel antenna, component description	GF40.15-P-5125TR
Wheel sensor, component description	GF40.15-P-5126TR
System activation button, component description	GF40.15-P-5127TR