Help in analysing noticeable symptoms with regard to the parking aid

This document serves to help analyse noticeable symptoms with regard to the parking aid.

Influences due to faults in the vehicle that cannot be detected by the PDC control unit

The function of the parking aid can be disrupted by faults in the vehicle that are not detected by the PDC control unit.

The following questions help to localise possible causes:

1. Are all the ultrasonic sensors fitted correctly?
   
   • The ultrasonic sensors must be firmly seated and locked in place in the bracket.
     
   • The ultrasonic sensor must be seated centrically in the bracket or in the bumper opening.
     
   • The angle of radiation of the ultrasonic sensors must be correct (conditional on the position of the bracket in the bumper and the bumper itself).
     
   • The cables to the ultrasonic sensors must not be under tension. (At low temperatures, tensile stresses might increase and can lead to cable damage.)
     
2. Is the PDC control unit correctly coded and programmed?
   
3. Are the following components that might be related to the parking aid free of faults?
   
   • Reverse signal
     
   • PDC button
     
   • Loudspeakers, acoustic signal
     
   • Screen, instrument cluster, head unit
     
   • Back-up camera
     
   • Other environment detection systems
     

Influences from body styling parts on the vehicle

Body styling parts on the vehicle can lead to reflection of the ultrasound signals and thus to unwanted detection of obstacles.

The following questions help to localise possible causes:

1. Are additional body styling parts fitted to the vehicle?
   Examples of additional body styling parts:
   
   • Exterior-fitted spare wheel
     
   • Additional headlights
     
   • Additional bumpers
     
   • Bicycle racks
     
   • Extended exhaust tailpipes
     
   If necessary, remove additional body styling parts and check the function of the parking aid once again.
   
2. Is a trailer coupling fitted?
   If necessary, check the trailer coupling for compatibility with the vehicle and that it is correctly fitted.
   Check whether the protective cap on the ball end of the trailer coupling is correctly fitted. (Fit the protective cap firmly until it locks into place. Only use original protective caps.)
   
3. Are the licence plate and licence plate holder correctly fitted? Is a non-matching licence plate holder fitted (the licence plate holder must not protrude beyond the mounting)?
   If necessary, remove the licence plate holder and check the function of the parking aid once again.
   

Influences from environmental conditions

The function of the parking aid can be disrupted by environmental influences.

Possible causes of malfunctions due to environmental influences are:

1. Soiling of the ultrasonic sensors
   
2. Foreign bodies between membrane and body of the ultrasonic sensor (e.g. gravel, insects)
   
3. Ultrasonic sensors freezing over at low minus temperatures
   
   • Ice or dew on the membrane
     
   • Ice between the membrane and housing
     
   • 'Bridge of ice' between membrane and housing
     
   • Freezing on residual water after washing vehicle at low minus temperatures
     
4. Splashing water during heavy rain
   

Influences from the vehicle environment

The function of the parking aid can be disrupted by the following influences from the vehicle environment:

1. During a function test of the parking aid, no obstacles may be located in the following areas:
   
   • In front of and behind the vehicle at least 2 m gap
     
   • To the side of the vehicle at least 1 m gap
     
   Under certain circumstances, bumps, ridges and gutters in the ground can be detected as obstacles.
   
2. In extreme cases, ground surfaces with good reflection properties can be detected as an obstacle. These include:
   
   • Cobblestones
     
   • Ground surfaces with lateral grooves
     
   • Ground surfaces with gutters
     
   • Ground surfaces with railway or tram lines
     
   • Ground surfaces with potholes
     
   • Gravel
     
3. Certain forms of terrain can be detected as obstacles depending on the vehicle position. These include:
   
   • Bends
     
   • Dips
     
   • Ramps
     
   • 'Sleeping policemen'
     
   The effect is amplified on wet roads.
   
4. Heavy clouds of exhaust gas or heat in the detection range of the parking aid can cause bogus obstacle detection in extreme cases.
   The following conditions can contribute to bogus obstacle detection:
   
   • Exhaust gas stream with strong acceleration
     
   • Exhaust gas stream at low outside temperatures
     
   • Exhaust pipe outflow strikes an obstacle (e.g. wall, other vehicle)
     
   • Vehicle with hot engine remains at standstill and heat cloud forms in the detection range of the parking aid
     
5. Ultrasound sources in the vehicle environment can influence the function of the parking aid. These include:
   
   • Compresses air devices such as impact screwdrivers, compressors etc.
     
   • Cleaning equipment (e.g. steam cleaners)
     
   • Running machines, loud engine noise, motorcycles, trucks
     
   • Tyre rolling noise from passing vehicles, in particular in rain and at high speeds
     
   • Heavy rain
     
6. EMC interference sources in the vehicle environment can also influence the function of the parking aid. These include:
   
   • Chargers
     
   • Induction loops
     
   • Clocked fluorescent tubes
     
   • Garage door drives
     
   • Electrical machines
     

Hard-to-detect obstacles

Due to factors inherent in the system, the parking aid has difficulty detecting the following obstacles:

1. Snow-covered obstacles, in particular powder snow (the ultrasonic signal might be absorbed)
   
2. Obstacles with porous surfaces (the ultrasonic signal might be absorbed)
   
3. Obstacles with smooth surfaces (the ultrasonic signal might not be reflected to the ultrasonic sensor)
   
4. Obstacles in the short range at less than 20 cm distance
   When the continuous tone is reached at 30 cm gap, always stop immediately!
   
5. Under certain circumstances, low obstacles, even if they have already been detected, can disappear from the detection range of the parking aid when they are approached.
   This applies in particular if the ultrasonic sensors are installed in a high position.