Tire Pressure Monitor, Function - GF40.15-P-0001GW
Model 463
as of model year 2013
with code RY6 (Tire pressure monitoring system)
Shown on model 463 (except 463.342) up to model year 2019, model 463.342
Shown on model 463 (except 463.342) as of model year 2019
Function requirements, general
- Terminal 15 ON
The electronic ignition lock control unit sends the status of circuit 15 over suspension CAN 2 to the tire pressure monitoring system control unit or over the user interface CAN to the tire pressure monitoring system control unit.
TPM [RDK], general information
The tire pressure monitor (TPM) monitors the air pressure in the individual tires. A previously stored specified pressure for the front and rear wheels is used as a reference value. If a relevant loss of pressure occurs, the tire pressure monitor issues a warning message to the driver, when possible with the affected location. The measuring range of the tire pressure sensors is 0 to 6.375 bar.
The TPM [RDK] comprises the following subfunctions:
- Tire pressure sensing
- Warning messages
- Manual restart
- Automatic fill detection (except code ZU8 (USA version) up to model year 2015)
- Automatic teach-in process for tire pressure monitor control unit
Control unit power-down
After switching off the ignition the tire pressure monitoring system control unit remains active for 19 minutes and it can receive signals from the tire pressure sensors.
Tire pressure sensing
The tire pressure monitor (RDK) continuously monitors the tire pressure for all rotating wheels, while driving. The tire pressure sensors send data telegrams every 60 s via radio frequency to the tire pressure monitoring system control unit. These data telegrams contain the tire pressure, tire air temperature, wheel identifier (wheel ID) and the status information (e.g. direction of rotation).
In addition, the tire pressure monitoring control unit incorporates the outside temperature and the vehicle speed into the warning logic. The outside temperature is recorded by the outside temperature sensor. The SAM control unit or the front SAM control unit reads in the signals from the outside temperature sensor directly, calculates the outside temperature and sends them over the interior CAN to the instrument cluster or over the interior CAN, electronic ignition lock control unit and the user interface CAN to the instrument cluster. The instrument cluster calculates the display values and sends information on the displayed outside temperature and the displayed vehicle speed over suspension CAN 2 to the tire pressure monitoring system control unit or over the user interface CAN to the tire pressure monitoring system control unit.
Warning messages
The control unit tire pressure monitoring system continuously evaluates the data telegrams of the tire pressure sensors. If a relevant loss of pressure is detected at a tire, the tire pressure monitor control unit forwards the request to display a warning message over suspension CAN 2 to the instrument cluster or over the user interface CAN to the instrument cluster.
The instrument cluster shows the warning message and actuates the tire pressure monitoring system warning lamp.
A distinction is made between the following types of warning messages:
- Soft warning
- Hard warning
- Leak detection (rapid pressure loss)
Soft warning
The soft warning is shown immediately (as of model year 2015) or it is shown immediately after a journey has ended (Ignition OFF) (up to model year 2015).
Tires lose air over the course of time through diffusion. Therefore, the driver is notified in good time about the need to correct the tire pressures.
Warning threshold for soft warning:
- As of model year 2015
- Pressure loss of more than 12 % for longer than 8 minutes (except code ZU8 (USA version))
- Pressure loss of more than 12 % for longer than 18 minutes (with code ZU8 (USA version))
- Up to model year 2015
- Pressure loss of more than 0.25 bar for longer than 12 minutes
If, during a journey, the tire pressure on a wheel permanently drops below the warning threshold, a warning tone is issued. The tire pressure monitoring system control unit stores the measured pressure values and actuates a soft warning output.
Warning messages are canceled if one of the following events occurs:
- Fill up to the specified pressure
- Successful automatic fill detection (except CODE ZU8 USA version)
- Manual restart
Hard warning
A hard warning when driving notifies the driver of any significant and safety-relevant pressure loss.
If, during a journey, a pressure loss of more than 20 % is detected at a tire, the tire pressure monitoring system control unit issues a warning message after 5 minutes. During the subsequent driving cycles, the tire pressure monitor warning lamp remains actuated until the problem is rectified.
Warning messages are canceled if one of the following events occurs:
- Fill up to the specified pressure
- Manual restart
Leak detection (rapid pressure loss)
If a progressive pressure loss is detected over a certain period (gradient) of time while driving, it is assumed that a tire is defective. In this case a warning is triggered even before the triggering criterion for the hard warning is reached. The warning is generally issued at the latest 120 s after the start of a pressure loss of 0.2 bar/min and it is shown in the instrument cluster.
Warning messages are canceled if one of the following events occurs:
- Fill up to the specified pressure
- Successful automatic fill detection (except CODE ZU8 USA version)
- Manual restart
Manual restart
When the TPM [RDK] is restarted, the tire pressures set by the driver are adopted by the tire pressure monitoring control unit as the new specified values. The warning thresholds are redefined based on these pressure values.
The restart is in the "Service/tire pressure" menu in the instrument cluster is activated. The instrument cluster sends the "Activate TPM [RDK]" request over suspension CAN 2 to the tire pressure monitoring system control unit or over the user interface CAN to the tire pressure monitoring system control unit.
The tire pressure monitor control unit monitors the new pressure values for 5 min as from the start of the journey and checks them for plausibility. The medium pressure value on each axle is then stored as the new specified value for pressure monitoring.
Automatic fill detection (except code ZU8 (USA version) up to model year 2015)
An automatic fill detection is conducted, when at the start of a journey a change in pressure of more than 0.2 bar was detected on at least 2 wheels. For comparison, temperature-compensated and filtered pressure values are drawn on and compared against the values for the last journey.
After approx. 5 minutes of driving and a successful plausibility check, the new tire pressures are automatically adopted as specified values. A pressure difference between the right and left wheel of more than 0.5 bar is deemed to be implausible.
Automatic teach-in process for tire pressure monitor control unit
Following a parking period of more than 19 minutes, the automatic detection and localization of the tire pressure sensors is started when the journey starts.
A new tire pressure sensor undergoes automatic teach-in after a maximum of 10 minutes driving. Side localization is conducted by evaluating the rolling direction, based on right-left information from the tire pressure sensors.
During axle allocation, the reception level for the transmit signals of the tire pressure sensors is evaluated. The reception levels for the tire pressure sensors on the rear axle are greater than on the front axle.
If the tire pressure monitoring system control unit has been replaced, an initial startup must be performed using the diagnostic tester.
If it is necessary for tire pressure sensors to undergo teach-in, the teach-in process can be conducted using the diagnostic tester in the "Control unit adaptation" menu, and the "Write wheel electronics identification number" submenu.
As a consequence of the manually-conducted reduction in tire pressure, the successive deflation induces the tire pressure sensors to send a data log, which can then be used to read out a wheel ID.
If the Trigger tool is used, the individual tire pressure sensors have to be triggered one after the other to ensure that the corresponding data protocol is sent from which the required wheel ID can then be read out.
| Electrical function diagram for tire pressure monitor (TPM [RDK]) | Model 463 (except 463.342) as of model year 2013 up to model year 2019 with code RY6 (Tire pressure monitoring system) Model | PE40.15-P-2050-97ZGA | |
| 463.342 as of model year 2017 with code RY6 (Tire pressure monitoring system) Model 463 (except 463.342) as of model year 2019 with code RY6 (Tire pressure monitoring system) |
PE40.15-P-2050-97ZGB | ||
| Overview of system components for tire pressure monitor (RDK) | GF40.15-P-9999GW |