GF40.15-P-0001SK Tire Pressure Monitor Function

GF40.15-P-0001SK Tire pressure monitor function
- with CODE (470) Tire pressure monitor (base)

Component Identification:

Function requirements
^ Circuit 15 On
^ Tire pressure monitor (TPM [RDK]) system functional

General information
The TPM [RDK] system assists the driver in checking the tire inflation pressure thus contributing to active safety.

The TPM [RDK] system monitors the air pressure in the individual tires. A previously stored tire pressure is used as a comparative value. In the event of a relevant pressure loss a warning message is issued to the driver.

The tire pressure measuring range extends from p = 0 and 5.5 bar.

The TPM [RDK] comprises the following subfunctions:
^ Tire pressure sensing
^ warning messages
^ Manual restart

Tire pressure sensing
The TPM [RDK] control unit is permanently operational. Each time CAN-B awakes the TPM [RDK] control unit performs a reinitialization. While driving, the TPM [RDK] control unit continuously monitors the tire pressure of all rotating wheels (with terminal 15 Off for a further t = 19 min).

The TPM wheel sensors transmit data telegrams every t = 60 s while driving. These data telegrams contain the pressure, tire pressure temperature, individual serial number and status information (manufacturer, direction of rotation, operating mode etc.). The data are conveyed via two-way radio to the TPM [RDK] control unit.

In addition the TPM [RDK] control unit takes into account the outside temperature and the vehicle speed for the tire pressure determination. These data are provided via CAN B. The vehicle speed is transmitted by the instrument cluster.

The outside temperature is recorded by the outside temperature display temperature sensor and transmitted by the driver SAM control unit.

Any function faults or system faults are shown in the upper multifunction display (A1p13) in the instrument cluster.

Warning messages
A warning is issued when a relevant loss of pressure has been detected in at least one of the tires. The warning is issued without any position data.

The driver receives the feedback via the upper multifunction display in the instrument cluster or via the tire pressure monitor warning lamp (Ale66).

A differentiation is made between two types of warning messages:
^ Soft warning
^ Hard warning

Soft warning

The warning is issued immediately after a journey is ended (circuit 15 OFF).

Tires lose air over the course of time through diffusion. This is why convenient feature provides the driver with a message in good time about the need to correct tire pressures.

Warning threshold:
^ Pressure loss from p > 0.25 bar

If the tire pressure drops below the warning threshold for t > 12 min, a warning signal is set, stored in the memory of the TPM [RDK] control unit and displayed in the instrument cluster after terminal 15 Off.

If, during this period, the tire pressure increases again to min. 0.1 bar under the stored comparative value, the warning message is suppressed.

Warning cancellation:
^ Warning threshold no longer dropped below
^ Manual restart

Hard warning

While driving the hard warning informs the driver of a significant pressure loss which is relevant to safety.

Warning threshold:
^ Pressure loss of 20% or p ≥0.5bar

At a pressure loss of p < 0.7 bar the warning message display is delayed for t = 5 min. If, during this period, the tire pressure increases again to min. 0.2 bar under the stored comparative value, the warning message is suppressed.

At a pressure loss of p > 0.7 bar the tire pressure monitor warning lamp lights up immediately and the warning message appears in the upper multifunction display.

In the event of a leak detection (pressure drop p > 0.2 bar/min) the warning message is already output before reaching the warning threshold. The tire pressure monitor warning lamp is however first actuated when the permissible pressure loss is exceeded or on the next ignition sequence.

Warning cancellation:

When the ignition is switched on again (circuit 15 ON) the tire pressure monitor warning lamp is initially actuated again. The warning is canceled by a manual restart.

Manual restart
Via the left multifunction steering wheel button group and right multifunction steering wheel button group the tire pressure to be monitored can be reactivated via the tire pressure monitoring system menu in the instrument cluster.

The signals are read in by the steering column module via LIN and transmitted to the instrument cluster via CAN B. The pressure thresholds for the warnings are determined on the basis of the pressure values at the time of the restart. Operation feedback is issued immediately over the instrument cluster.

The TPM [RDK] control unit filters the new pressure values for t = 5 min as of the start of the journey and checks them for plausibility.

With new wheels or a longer parking time of t > 19 min first the separate wheel detection and axle assignment must be completed via the TPM wheel sensors.