Collision Avoidance and Parking Assist Systems: Description and Operation

Parking Aid PDC Park Distance Control

The parking aid PDC supports the driver on maneuvering into and out of parking spaces: signal tones and a visible indicator indicate the current distance to an obstacle. The signal functions of the PDC are:
- acoustic signal via radio speakers
- visible indicator via Control Display
- Fault signals in the check control (in the instrument cluster) and via Control Display

The shorter the distance to the obstruction, the faster the sequence of the individual tones. A distance below approx. 10 in (25 cm) is signaled by a continuous tone.

If the vehicle is moved along the side of a wall, the continuous tone of the distance warning is deactivated to avoid distracting the driver. If the vehicle continues to approach the wall, the distance warning is reactivated.

IMPORTANT: responsibility on the part of the driver
PDC is unable to replace the personal assessment of obstacles. Sensors have a blind spot. In this blind spot, it is no longer possible to detect objects. The detection of obstacles can reach the limits of physical ultrasonic measurement, e.g. in the case of trailer towbars and trailer hitches or thin and painted objects. Low obstacles that have already been indicated can "disappear" again before a continuous tone is sounded (e.g. a high edge of the curb).

For this reason, the assessment of obstacles, even with PDC, is the responsibility of the driver.

Brief description of components

PDC button
The park distance control can be switched on and off manually with the PDC button.

The PDC button is mounted to the left of the start/stop button. The PDC button consists of
- Button
- Indicator lamp for the function display (LED)
- Locating light (LED)

The indicator lamp in the PDC button indicates
- that the PDC system is activated: when the PDC system is activated, the indicator lamp in the PDC button lights up. The indicator lamp goes out when the system is switched off.
- When there is a fault in the PDC system: when there is currently a fault in the system, the indicator lamp flashes.

Front ultrasonic converters
The distance between the vehicle and the obstacle is measured by ultrasonic converters in the bumpers.

The distance between the vehicle and an obstruction is monitored in accordance with the sonar principle. The ultrasonic converters emit an ultrasonic signal. This ultrasonic signal is reflected by obstacles. The ultrasonic converters receive these echoes, amplify them and convert them into a digital signal. The digital signals are sent across the data line to the PDC control module.

The control module compares the data of the individual ultrasonic converters and calculates the shortest distance between the ultrasonic converters and the obstacle.

The measuring range of the ultrasonic converters lies between approx. 8 in (20 cm) and a maximum of approx. 60 in (150 cm). If the minimum detectable distance increases beyond the permissible extent, a fault code is stored in the fault memory. Soiling, moisture, ice and snow can lead to an increase in the minimum detectable distance beyond the permitted level.

Each ultrasonic converter has its own electronic component, its own voltage supply and its own data link to the PDC control module.

Four ultrasonic converters are mounted in the front bumper
- front left
- front right
- front center (two ultrasonic converters)

Rear ultrasonic converters
The rear ultrasonic converters function in the same way as the front ultrasonic converters.

Four ultrasonic converters are mounted in the rear bumper
- rear left
- rear right
- rear center (two ultrasonic converters)
If the PDC control module detects that a trailer has been hitched and electrically connected, the rear ultrasonic converters are deactivated.

PDC control module
The PDC control module is located in the rear of the luggage compartment on the right.

The PDC control module receives the information on the switch-on/off conditions of the system via the K-CAN bus system:
- Reverse gear engaged;
- Trailer operation: the PDC control module receives the status signal of the trailer from the trailer module via the K-CAN bus system.
- Road speed,
- PDC button pressed.

The PDC control module
- activates the ultrasonic converters, receives the echoes,
- evaluates the received echo impulses,
- monitors the correct function of the ultrasonic converters,
- activates the PDC indicator lamp,
- activates the audio system controller control module. The audio system controller activates the acoustic distance warning via the loudspeakers (K-CAN bus system);
- activates the Control Display for visual output of the distance warning (K-CAN bus system),
- activates the reversing gong (country-specific version for Japan).
- displays error messages of the PDC in the check control of the instrument cluster.

Other control modules that are important for the PDC
Various other control modules in the composite system are involved in the distance warning function:
- KOMBI in the instrument cluster: The KOMBI control module provides the outside temperature and mileage reading.

Outside temperature: ice and dew can lead to activation of the ultrasonic converters where it is not required. The response characteristics of the ultrasonic converters change depending on the outside temperature: the PDC control module regulates the modified response characteristics at an outside temperature of 43 degrees F (6 degrees C) and lower.

Km reading: in the case of a fault code entry in the fault memory, the mileage reading and the outside temperature are also stored.

- DSC (Dynamic Stability Control): The DSC control module provides the travel distance and speed signal.
- AHM (Trailer Module): The AHM control module reports the trailer status. If a trailer is electrically connected, the rear ultrasonic converters are deactivated.
- EGS (Electronic Transmission Control): The EGS control module provides the reverse gear signal for automatic activation of the PDC.
- CAS (Car Access System): The CAS control module reports the terminal status to the PDC control module.

Terminal R ON With terminal R on, the CAS transmits the information "Terminal R ON" via the data buses to the control modules.

Terminal 15 wake-up: The CAS activates terminal 15 wake-up for all control modules of the PT CAN

- PM (Power Module): The PM control module provides the battery voltage.

Audio System Controller, ASK
The PDC control module only provides the distance indications between the ultrasonic converters and the obstacle. From this, the ASK calculates the tone sequence of the acoustic distance warning.

The acoustic distance warning overrides the audio sound.

Rear radio speakers
The distance warning for reversing is output via the rear loudspeakers.

The rear loudspeakers are activated by the Audio System Controller (ASK). Signal path: PDC control module -> K-CAN bus system -> Control Display -> Audio System Controller ASK -> DSP amplifier -> rear loudspeakers.

Front radio speakers and acoustic generator
The front distance warning is output, depending on the coding, via
- gong in the Control Display: Signal path: PDC control module -> K-CAN bus system -> Control Display -> Gong
- Front loudspeakers: Signal path: PDC control module -> K-CAN bus system -> Control Display -> Audio System Controller ASK -> front loudspeakers

If faults have occurred, a warning tone is also issued.

Control Display
The distance to an obstacle can also be displayed visually in the Control Display. If an obstacle is further away, it is displayed in the Control Display before a sound signal is issued (green display).

Displaying the distance: in the Control Display, select "Configuration". Press "PDC image". The PDC indicator appears as soon as the PDC is switched on automatically or manually. The PDC indicator overrides other displays. When the PDC system is switched off again, the previous display appears automatically in the Control Display.

Main functions

Switch-on/off conditions of the PDC parking aid
The PDC parking aid is switched on when the driver
- presses the PDC button (manual activation of the PDC) or
- engages reverse gear (automatic activation of the PDC).

The PDC parking aid is switched off
- when the driver presses the PDC button (manual) or
- switches off the ignition (automatic);
- after a distance driven of approx. 165 ft (50 m) or
- after a speed of approx. 20 mph (30 km/h) is exceeded.
- During trailer operation, the rear ultrasonic converters are deactivated.

Circumstances representing problems for the switch-on/off conditions
In borderline situations, the PDC system can signal the presence of obstacles although none are in fact present. Or obstacles that are present are not detected:

Problem case: The PDC system signals the presence of an obstacle where there is none:
In the following situations, it is possible that the ultrasonic converters signal a non-existent obstruction:
- When the ultrasonic converters are not mounted correctly in their support brackets.
- During heavy rain
- If the ultrasonic converters are extremely dirty, iced up or covered with snow
- In the case of ground echoes from extremely rough road surfaces or grasses
- In large, closed, rectangular rooms with very smooth walls (e.g. underground car parks)

Problem case: The PDC system does not detect the presence of an obstacle:
In the following situations, it is possible that the ultrasonic converters do not detect an obstruction:
- Low objects with corners and sharp edges
- Automatic deactivation of the PDC when driving alongside a wall: The acoustic signal is always switched off when the driver is attempting to park alongside a wall. This also applies when the vehicle approaches an obstruction-but further away-at a different angle. There is a danger of driving into this obstacle.

Warning in the event of a fault
When there is currently a fault in the PDC system,
- the indicator lamp in the PDC button flashes,
- there is immediately a continuous tone when the driver presses the PDC button.
- The check control in the instrument cluster issues an error message.

The system can not be switched on.

Service functions

Procedure for troubleshooting

IMPORTANT: Prior to troubleshooting, first check the mechanical condition of the ultrasonic converters:
Particular care must be taken before starting extensive troubleshooting to ensure that the converters are mounted correctly in their retaining fixtures and are free of dirt.

IMPORTANT: avoid new influencing variables during troubleshooting:
During troubleshooting there should be no obstruction closer than 16 in (40 cm) to the converter. An obstacle in the immediate proximity of the ultrasonic converters changes the characteristics of the PDC system.

Note on safety
Keep the ultrasonic converters clean and free of ice to ensure their full operational capability.

Do not direct high-pressure cleaners directly at the ultrasonic converters. Always keep a distance of at least 4 in (10 cm).

Country-specific version

Japan: reversing gong and distance warning
An acoustic signal is output via the gong for as long as reverse gear is engaged. The reversing gong is switched off immediately if the PDC detects an obstruction within its measuring range and issues a distance warning.