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

MODEL 463.236 up to 31.5.12 with CODE (RY6) Tire pressure monitor (TPM) as of Model Year 2009 / YoM 08 

MODEL 463.248 /270 /341 up to 31.5.12 with CODE (RY6) Tire pressure monitor (TPM) as of Model Year 2007 Model year 07.5, Modification year 07 

MODEL 463.237 up to 31.5.12 as of Model Year 2009 / YoM 08 

MODEL 463.249 /271 up to 31.5.12 as of Model Year 2007 Model year 07.5, Modification year 07 

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 tire pressure monitoring system monitors the air pressure and tire air temperature 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 measuring range of the tire inflation pressure extends between p = 1 and 6.5 bar.

The TPM [RDK] comprises the following subfunctions: 

• Tire pressure sensing
• Warning messages
• Manual restart
• Automatic fill detection

Tire pressure sensing function sequence 

The tire pressure monitor control unit is permanently operational. Each time the interior CAN is activated the tire pressure monitor control unit runs a re-initialization routine.

During a journey the TPM [RDK] system continuously monitors the tire pressure of all rotating wheels (for circuit 15 OFF for t = 19 min).

While driving the tire pressure sensors transmit six data messages every t = 60 s.

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 transmitted by radio to the tire pressure monitor control unit.

When sensing the tire pressures the tire pressure monitor control unit also takes the outside temperature and vehicle speed into consideration. The data are sent over interior CAN.

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 front SAM.

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

Warning message function sequence 

Messages relevant to the tire pressure monitoring system take place automatically in the multifunction display. The warning messages show the driver that the air pressure has dropped in at least one wheel. This type of warning can be erased in the same ignition sequence when the tire pressure monitor control unit detects that the triggering cause no longer applies (e.g. air has been refilled). In the event of a warning message (tire air pressure loss in one or more tires) a corresponding entry is made in the diagnosis message memory. Information messages indicate to the driver that the system function is faulty.

If a warning relevant to function (fault message) is displayed, a corresponding entry must be present in the diagnosis fault memory.

The fault display remains active for the entire ignition sequence.

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 tire pressure monitor control unit and shown in the multifunction display 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
• Successful automatic fill detection
• 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 ≥0.5 bar

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.

A warning message appears immediately in the multifunction display in the event of a pressure loss p > 0.7 bar.

If a leak is detected (air extraction p > 0.2 bar/min) the warning message is issued before the warning threshold is reached.

Warning cancellation:

The warning is first shown again in the multifunction display in the event of an ignition restart (terminal 15 On).

The warning is canceled by a successful automatic fill detection or a manual reactivation restart.

Manual restart function sequence 

Via the 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 the interior CAN. 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 tire pressure monitor control unit filters the new pressure values for t = 5 min from the start of the journey and checks their plausibility.

Where new wheels are concerned or where a vehicle has been stationary for t > 19 min. the automatic wheel detection and axle assignment have to be disconnected first over the tire pressure sensor.

Automatic fill detection function sequence 

Automatic fill detection is performed if a change in pressure of more than p = 0.2 bar was detected on at least two of the wheels. Temperature-compensated and filtered pressure values can be used here for comparison.

The new reference values are stored if the plausibility check is passed.

	Tire pressure monitor (TPM [RDK]) location of components		GF40.15-P-0001-06G
	Tire pressure monitor (TPM [RDK]) block diagram		GF40.15-P-0001-07G
	Tire pressure monitor (TPM [RDK]) messages		GF40.15-P-0001-08G
	Instrument cluster, component description	A1 Model 463.236/237 Model 463.248/249 up to 31.8.08 as of Model year 2007 Model year 07.5, modification year 07 Model 463.270/271/341 as of Model 2007 Model year 07.5, modification year 07	GF54.30-P-6000G
	Wheel sensor, component description	A69/1, A69/2, A69/3 and A69/4	GF40.15-P-5126G
	Component description for the outside temperature display temperature sensor	B14 Model 463.236/237 Model 463.248/249 up to 31.8.08 as of Model year 2007 Model year 07.5, modification year 07 Model 463.270/271/341 as of Model year 2007 Model year 07.5, modification year 07	GF83.57-P-4002G
	Front SAM control unit with fuse and relay module, component description	N10/1 Model 463.236 / 237 Model 463.248/249 up to 31.8.08 as of Model year 2007 Model 463.270/271/341 as of Model year 2007	GF54.21-P-6070G
	Electronic ignition/starter switch control unit (EIS), component description	N73 Model 463.236/237 Model 463.248/249 up to 31.8.08 Model 463.270/271/341 as of Model year 2007	GF80.57-P-6000G
	Steering column tube module, component description	N80 Model 463.236/237 Model 463.248/249 up to 31.8.08 as of Model year 2007 Model 463.270/271/341 as of Model year 2007	GF54.21-P-6050G
	Tire pressure monitor control unit, component description	N88	GF40.15-P-5124G
	LIN converter, component description	N135	GF82.90-P-4023G
	Multifunction steering wheel button group, component description	S110, S111	GF82.90-P-4001G