Brake Light Signal

Tire Defect Indicator (RPA)

The tire defect indicator (RPA) is designed to monitor the tire status while driving. The ABS speed sensors monitor the four wheel speeds independently of one another. The control module evaluates the speed signals and makes the corresponding information available to the driver as required, thus informing the driver of a possible tire defect.

Description
The abbreviation for the tire failure warning system has changed: New: RPA old: DWS

Brief description of components

Control module
The control module is a microprocessor-controlled system. It is supplied with power and activated via terminal 15. The control module is fitted in the instrument panel support member behind the glove compartment.

Calibration button
The calibration button is located in the dashboard.

ABS speed sensor
Already fitted.

Wiring harness
The wiring harness is equipped with an 18-pin connector that contains all the supply, signal and bus leads for the control module.

Function
The system is designed to monitor the tire status while driving. Loss of pressure in a tire reduces the rolling circumference of the wheel. This increases the rotation speed of this wheel. The Tire defect indicator measures the wheel speeds and sets up a comparison of the diagonally opposed wheels and the average speed, thus detecting air pressure loss. In this context, extreme driving situations such as strong acceleration or fast cornering are detected and corrected by the software. The system provides information as of 15 km/h minimum speed. The ABS speed sensors determine the wheel speed signals and send them via the DSC control module to the RPA control module. The tire pressure to be monitored is specified by the driver. Using the calibration button, the driver instructs the system to adopt the current set of wheels with the selected tire pressure as the set reference. Within the framework of the calibration process, the system automatically learns the tire reference status. Depending on driving style and conditions, the learning process can take between 45 minutes and several hours. However, the system is already armed for warnings after 10 minutes and can detect air-pressure losses of 50%. As the calibration continues, the warning thresholds are increased to 30% ± 10% of the cold air pressure. The instrument cluster informs the driver about the operating status of the Tire Failure Warning System.

Messages to driver

Display "Puncture" in instrument cluster (with CC text display) or RPA indicator lamp in the instrument cluster lights up red
The system has discovered a flattening of a tire. The flattening lies above the defined limit values (see function).

Display "Tire monitoring inactive" in instrument cluster (with CC text display) or RPA indicator lamp in the instrument cluster lights up yellow
A malfunction of the system detected by the RPA control module. A deactivation of the system by touching the calibration button on the E39 M5. In the case of deactivation, the output of a warning message is suppressed.

Display "Tire pressure set" in instrument cluster (with CC text display) or RPA indicator lamp in the instrument cluster lights up yellow for 16 seconds
Pressing the calibration button for six seconds starts the calibration procedure. Here, the ignition must be on and the engine off.

IMPORTANT: Calibration must be performed every time the cold air pressure, the wheel position or the set of wheels are changed. If this is not the case, a false alarm can occur.