Distance sensors

Distance sensors

The four distance sensors are located in the rear bumper. They are mounted in identical plastic brackets that can be interchanged.

The sensors are named as follows:

•	Left-hand outer distance sensor (RL)

•	Left-hand centre distance sensor (RLC)

•	Right-hand centre distance sensor (RRC)

•	Right-hand outer distance sensor (RR)

Each distance sensor contains a diaphragm that works both as a speaker unit and microphone unit.

The distance sensors emit a wide-angle ultrasound signal (120° laterally and 60° vertically) and detect the reflected sound signals. The signals are converted to a digital signal that is sent to the control module for calculation of the closest object.

The distance sensors are active when the control module is in mode 2 or 3, i.e. Active and Detected

The distance sensors work according to a loop (controlled by the control module), which is repeated 3 times per second. The loop is as follows:

-	Step 1: Sensor 1 - RL - emits an ultrasound signal and listens with sensors 1 and 2.

-	Step 2: Sensor 2 - RLC - emits an ultrasound signal and listens with sensors 1 and 2.

-	Step 3: Sensor 2 - RLC - emits an ultrasound signal and listens with sensors 2 and 3.

-	Step 4: Sensor 3 - RRC - emits an ultrasound signal and listens with sensors 2 and 3.

-	Step 5: Sensor 3 - RRC - emits an ultrasound signal and listens with sensors 3 and 4.

-	Step 6: Sensor 4 - RR - emits an ultrasound signal and listens with sensors 3 and 4.

After a completed loop, the control module checks the sensors and calculates using Pythagoras' theorem (a ² +b ² =c ² ) which object is closest to the rear or side of the car, i.e. the object that the driver will be informed of.

Diagnostics

The control module monitors its own functionality and inputs and outputs.

The distance sensors are checked 10 times/second in modes 2 and 3.

In the event of a fault in a distance sensor or its communication with the control module, the following diagnostic trouble codes are generated:

Diagnostic trouble code	Sensor
B2906 B2916 B2926 B2936	RR RRC RLC RL	Communication cable shorted to B+
B2907 B2917 B2927 B2937	RR RRC RLC RL	Communication cable broken or shorted to ground, or break in supply
B2908 B2918 B2928 B2938	RR RRC RLC RL	Open ground circuit, short to ground or B+, or internal sensor error
B2909 B2919 B2929 B2939	RR RRC RLC RL	Internal fault
B2950	Sensor power supply shorted to ground

-	RR: Right-hand outer sensor

-	RRC: Right-hand centre sensor

-	RLC: Left-hand centre sensor

-	RL: Left-hand outer sensor

For further information about fault diagnosis, see

Fault diagnosis strategy for electronic systems .