Overview:

The Park Distance Control (PDC) system is designed to make manoeuvring the vehicle much easier. By using ultrasonic sensors incorporated into the bumpers the system emits audible tones to alert the driver of an obstacle near the vehicle. Two versions are fitted to the Galaxy, a "low" system which monitors just the rearward direction and a "high" system which monitors both the front and rear of the vehicle. The system detects obstacles from 1.2meters down to 20cm with an additional 80cm field to the sides.

Operation:

The PDC system is only active when enabled and below a speed of around 10mph. It can be automatically switched on by engaging reverse gear or by pressing the switch on the dashboard. Once enabled the switch glows orange and the system can be disabled by pressing the switch a second time or driving about 10mph. Failure a fault is detected the system indicates this by a short beep and then a flashing switch when the system is turned on.

Components:

The Galaxy PDC system comprises the following 5 components:

• 4 or 8 parking sensors
• An ECU / Controller
• An activation switch on the dashboard
• A Front sounder which sits below the front passenger seat
• A Rear sounder which is the near side tailgate compartment

Depending on if you have rear assist only or front and rear assist you will have parking sensors embedded in both bumpers, on the rear bumper the sensors sit at the bottom in a valance strip whilst on the front they are integrated into the trim piece as seen here:


 

The control module sits under the passenger seat on a metal plate with the front sounder, its shown here out of the car for clarity along with the dashboard switch for vehicles with Front PDC:



 

Common Failures

There are three main causes of failure, the first is normally accompanied by an entirely dead system caused by the rear wash screen pipe joint in the passenger foot-well separating at a joint. Screen wash will then drain out and flood the storage area under the passenger seat submerging the controller in the process. Generally a new controller is required once this has happened but if caught early enough it may be possible to dry out the unit with no ill effects.

The second and third are coupled - and are by far the more common cause being a simple sensor fault. The system is designed to enter a fault mode and stop working as soon as just one sensor is faulty. Diagnosing is best done with the aid of VCDS / VagCom as it will pinpoint the exact sensor which is causing the problem and normally logs intermittent sensors as well. On the rear sensors the wiring behind the bumper can be so tight where it enters the sensors connector that over time it splits and breaks. If this is fine then the problem is more likely the sensor itself. If you don't have access to a fault code reader then a crude test is to activate the system and then put your ear to each sensor in turn - they emit ultrasonic in bursts which the human ear can perceive as a rhythmic ticking sound. This is a VERY basic test though as some faulty sensors still emit noises when faulty but in most cases the faulty sensor(s) can be identified this way

A far more complex test is using VCDS, in 90% of cases a faulty sensor will be logged and a simple check of the fault codes held by the PDC controller will reveal which sensor(s) are causing your problems. In some cases you may have to open the controller and then check the "measuring blocks" - Group 1 shows the front sensors, group 2 shows the rear sensors. The system MUST be active to view these figures, ie, reverse engaged or the switch depressed to engage. A value of 255 means the sensor in unable to detect anything within its field or the sensor is off - use an assistant or place the laptop so you can see it from outside the vehicle then walk around and stand next to each sensor in turn. You should see each sensor detect you as an obstacle with a low distance being shown in the measuring block - generally a value of around 20cm (+/- 2) is the lowest value you'll see as the sensors can't detect obstacles closer then this.

In this example the car is parked tight to a wall on the drivers side:


 

Wiring Diagram for the System: