Self-Test Function Sequence

The Following Components Are Checked For Proper Operation:

Sonar control unit
Sonar sensors
Parking assist electrical lines

Sonar Control Unit Self-test:

The sonar control unit performs a self test after the ignition is switched on (circuit 15 ON). In the process, the hardware of the sonar control unit is tested.
NOTE: The self-test is performed irrespective of the selector lever position of the automatic transmission.
The sonar system control unit carries out further self-tests at regular intervals.
The following states can be recorded here:
- Operational malfunction
- System error(s)
If a malfunction or system error occurs, the sonar system is deactivated and the LED in the sonar system switch in the upper control panel control unit lights up.
For this purpose, the sonar control unit sends a corresponding request to the upper control panel control unit via the CAN communication, electronic ignition switch control unit, CAN communication, BCM and battery sensor LIN. The upper control panel control unit then actuates the LED directly.

Sonar Sensor Self-test:

A self-test of the sonar sensors (e.g. for connection) is only performed when a sonar sensor is "pulsed" (ultrasonic transmitting).
NOTE: The self-test is performed irrespective The self-test is performed depending on the selector lever position of the automatic transmission and the speed.
Sonar sensor test for subsequent vibrations:
The test is performed cyclically.

Malfunction:

A malfunction can be caused by a temporary external disturbance (e.g. a jackhammer on a construction site, a steam jet or by driving through an automatic car wash). If the malfunction persists for a longer period of time, identification of the cause takes place during driving operation by means of a self-test. If the malfunction is still present, this is interpreted as a system error.

NOTE: A warning sound is not emitted.

System Error:

A system error can have the following causes:

Malfunctioning component
Error in communication
Over-voltage or under-voltage

If a system error or a malfunction in the sonar sensors is detected through a function test during operation, an error message is displayed on the display screen. The sonar control unit additionally sends a request to issue a warning tone to the display control unit via the CAN communication. The display control unit then actuates the warning buzzer directly. The display control unit issues a warning tone for t = 3 s, the sonar system switches itself off and a malfunction is entered in the DTC memory of the sonar control unit.

NOTE: The size of the license plate bracket attached to the bumper varies depending on the national version. Due to the different dimensions and shapes the sonar system must be adapted to the particular circumstances. A diagnostic tester can be used to code the national version to prevent malfunction caused by the license plate bracket.