System Description

Parking Assist System
The Park Assistent supports the driver when reversing. The system detects obstacles and indicates these to the driver in good time. If an obstacle is detected by the system, a signal tone with a tone break sounds at a distance of 1.5 m to the inside sensors and 0.6 m to outside sensors. The tone break of the signal tone shortens as the vehicle approaches the obstacle. At a distance of 0.3 m, a continuous tone is emitted.

System readiness
The Park Assistent signals readiness with a short signal tone provided that:
- the ignition is switched on
- reverse gear is engaged

System error
System errors are indicated by the sounding of a continuous tone after reverse gear has been engaged. This continuous tone differs from the continuous tone emitted when an obstacle is detected.

System components
The Park Assistent consists of:
- a control module which is located under the driver's seat together with a cover plate.
- four ultra-sound sensors which are installed in the rear spoiler.
- an audible signal transmitter which is integrated into the instrument cluster.


WARNING: Danger of injury and damage to vehicle when the vehicle is rolling backwards!

- Reverse gear must be engaged and the ignition must be switched on; otherwise the Park Assistent System is deactivated.


WARNING: Danger of injury and damage to vehicle when the system limits are reached! The system does not free the driver from his/her responsibility to be careful.


- Short obstacles such as a person lying down cannot be detected.
- The reflection capabilities of the system may be impaired by sound-absorbing obstacles such as powdery snow, and by sound- reflecting obstacles such as glass bottles.
- Very thin obstacles and obstacles with small reflecting surfaces cannot be detected.

Sensor signals
Every sensor emits an ultrasound beam with the following geometric specification.
- Horizontal beam angle = 120 °
- Vertical beam angle = 60 °

The control module measures the distance between the sensor and any obstacle in cyclical intervals. Measurement is based on echo-sounding techniques.
The sensors are actuated briefly at regular intervals and transmit ultrasonic waves. Next, the sensors are switched to receive mode, and receive the reflecting sound waves. The control module then calculates the distance between the sensor and the obstacle from the running time of the soundwaves.

Fig. 1:

Fig. 2:

Diagnosis
The following components are subject to cyclical monitoring when the ignition is on and the shift lever is in reverse gear:
- Control module supply voltage
- Sensor supply voltage
- Function of all sensors
- Function of control module
(transmission and reception pulses, EEPROM)


NOTE: External environmental conditions such as ice, snow or dirt can also adversely affect the function of the sensors and lead to a fault being stored.
The four sensors are connected to the control module via a wiring harness incorporated in the rear spoiler. To replace the sensors or to
perform tests, the rear spoiler must be removed.







Pull off plug on the sensor

If a sensor has to be replaced, the electrical plug connection must first be disconnected.

Procedure
1. Lift the lower tab carefully with your finger.
2. Pull out the plug.







NOTE: Dirty or frost-covered sensors lead to system malfunctions. However, in this case the errors are not stored. Instead, the same continuous tone is emitted as for obstacle detection. Once the cause of the malfunction has been eliminated, the system returns to its normal state and the continuous tone stops.