GF40.15-P-0002T Tire Pressure Loss Warning (RDW) Function
GF40.15-P-0002T Tire pressure loss warning (RDW) function
- 211 as of 1.6.04
- with CODE (477) Tire pressure loss warning
General
Tire pressure loss warning (RDW) is a system scope of the ESP, SPS [PML] and BAS control unit (N47-5). It manages without additional components. It is to warn the driver in the event of tire pressure loss before the tire runs flat due to puncture damage. The driver is warned about a pressure loss via the multifunction display (A1p13) in the instrument cluster (A1). The tire pressure monitor warning lamp (A1e66) in the instrument cluster (A1) is actuated in parallel with this.
Function
The rolling circumference depends on tire pressure. This dependency is evaluated in the ESP, SPS [PML] and BAS control unit (N47-5) by a comparison of the 4 wheel speeds. The ESP, SPS [PML] and BAS control unit (N47-5) compared between:
^ FL and RR wheel speeds
^ FR and RL wheel speeds
Furthermore, the following sensor signals are included in the calculation:
^ Lateral acceleration
^ Yaw rate
^ Wheel moment
Aim
A tire pressure loss in a wheel should be detected before it leads to tire damage.
The tires are monitored by the tire pressure loss warning (RDW) without detail of location.
The tire pressure loss warning (RDW) is only active from a minimum speed of approx. 20 km/h.
System properties
^ Detection of pressure loss after driving for a few minutes.
^ Active when driving straight-ahead (lateral acceleration < 1 m/s2).
^ Active when driving at a uniform speed (longitudinal acceleration < 1 m/s2).
^ Inactive with control intervention function (ABS, ASR, ESP).
^ Inactive with a large drive torque.
^ Inactive when braking.
^ Partially active with a low coefficient of friction, on rough roads, snow chains.
System limits:
^ Warning limit with a pressure loss of 30 to 50% at one wheel
^ Warning without details of location.
^ No detection of even diffusion losses.
^ Incorrect operation by the driver (reactivation despite significantly reduced pressure).
