GF40.15-P-2005SXA Detection of Pressure Loss, Function
GF40.15-P-2005SXA Detection of pressure loss, function
- with CODE (475) Tire pressure monitor (Siemens) [model 216.3, 221.1]
- with CODE (470) Tire pressure monitor (base) [model 216.3, 221.1]
- with CODE (494) USA version [model 216.3]
Pressure loss detection is subdivided into the following areas:
^ Detection of a slow pressure loss
^ Detection of a sudden pressure loss
Detection of a slow pressure loss
In the course of time each tire looses air e.g. through diffusion. As a comfort function the driver receives in good time from the tire pressure monitor (RDK) system information on the due correction of his tire pressures. The warning takes place while driving (hard warning) or immediately after driving (hard or soft warning). A temperature increase always leads to a pressure increase in the tire. In the TPM [RDK] control unit (N88) the temperature dependent pressure change in the tire is calculated and taken into account in the TPM system strategy.
A temperature change in the tire does not lead to erroneous warnings.
Soft warning (information message with yellow warning lamp)
The warning takes place in a temperature-compensated manner at a pressure loss of 0.25 bar compared with the stored filling pressure. The warning threshold is limited upwards to 0.2 bar under the filling pressure.
Warning cancellation:
The following conditions result in the warning being withdrawn:
^ The warning threshold is no longer dropped below
^ Filling detection was successful
^ Manual reactivation of the TPM system carried out
Checking the warning condition while driving
If the warning threshold is dropped below for a time of 12 minutes, a warning signal is stored in the memory of the TPM [RDK] control unit and with "terminal 15 OFF" in the instrument cluster (A1).
Hard warning (red warning lamp)
While driving, the hard warning indicates to the driver a distinct pressure loss which is relevant to safety. The warning corresponds to the requirements of the USA legislation.
Parameters for hard warning:
^ The warning ensues in the event of a pressure loss of 20 % or 0.5 bar compared with the stored filling pressure.
^ The warning threshold is limited downwards to the minimum pressure (1.5 bar).
^ The temperature compensation with hot tires is limited at a temperature of 40 degrees C above the ambient temperature. The warning threshold remains constant.
^ The warning threshold is limited upwards to 0.2 bar under the filling pressure.
The warning is suppressed during filling detection.
The tire pressure monitor warning lamp (A1e66) in the instrument cluster is activated at the same time as the "hard warning". It goes out after the TPM system is reactivated.
Warning cancellation:
After a hard warning with "terminal 15 ON" first the tire pressure monitor warning lamp is actuated again. The warning is canceled by a successful filling detection or manual reactivation.
Detection of a sudden pressure loss
If progressive pressure loss is detected during 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 triggering criterion for the hard warning is reached. As a rule the warning takes place at the latest 60 s after the start of a pressure loss of more than 0.2 bar/min and is shown as a red warning message in the multifunction display in the instrument cluster.
Warning cancellation:
During "terminal 15 ON" the warning can be canceled by a successful filling detection or by manual reactivation. After a leak warning with "terminal 15 ON" the tire pressure monitor warning lamp in the instrument cluster is activated first. If after the start of a journey new pressure values exist and no warning criterion is met, the tire pressure monitor warning lamp is switched off and the warning information erased. The warning is canceled when filling detection or a manual reactivation is successfully carried out.
