PDC shutdown: Why a car doesn’t recognise a trailer as an obstacle

30. Mai 2018 um 11:09

PDC shutdownFor some years now the PDC (Park Distance Control) system has been a standard feature of a car. When reversing sensors recognize obstacles behind the car, the board computer gives the driver an optical and/or acoustic signal.
In reality, a trailer should always be recognised as an obstacle, because it is directly at the tail end of the car. The PDC should really go haywire and permanently give warning signals. But it doesn’t – and why not? The reason is that the PDC shuts down, which is realised in various ways.
Heinz Hueber, Technical Manager of our Electrical Kit Department, explains how the Park Distance Control can be switched off with retro-fit trailer hitches and how the PDC shutdown functions.

1. Complete integration into the onboard electronics of the towing vehicle
If a towbar is installed by a car manufacturer in the factory, the electronics will be completely integrated with the onboard electronics of the towing car. Trailer operation is then activated in the board computer so that the board computer automatically knows when the trailer plug is inserted into the socket, e.g. that the car’s PDC and the rear fog light have to be switched off and possibly the trailer combination stabilisation switched on.
If a trailer hitch is retro-fitted the coupling electronics into the onboard electronics of the towing vehicle could also be integrated by a specialist workshop. For this, the control units in the vehicle must be manually activated with a tester (Caution! Not every tester can activate control units). There will be additional costs.
Unfortunately, not all car manufacturers authorise the access to the intelligent board electronics. Sometimes after a service at an authorized workshop the activation is reset. Therefore, the manufacturers of retro-fit trailer hitches solve the PDC shutdown by means of an electronic or mechanical trailer identification.

2. Control module in the electrical kit is used for recognition
A control module is built into the electrical kit delivered along with the towbar. This module detects the electrical load of the trailer lighting and passes on the information to the board electronics accordingly. Here we can latch into the board electronics of the towing vehicle, but without activation. The PDC shutdown is either switched on or off manually via a P-OFF switch, which many cars have, or automatically via an intelligent control module of the electrical kit, which also switches the trailer rear fog light on and off. Disadvantage: further driver assistance systems will not be adapted.

3. Micro-switch interrupts the power supply
The easiest solution is a mechanical micro-switch in the towbar socket. If the connector of the trailer is plugged in the micro-switch bumps off and interrupts the power supply to the PDC. At the same time the rear fog light will be switched off on the towing vehicle – only the rear fog light on the trailer will shine, not on the towing vehicle.

4. Digital communication via databus (CAN)
Nowadays many vehicles communicate via a databus. Here all information is digitally transported via a two-wire cable. The control modules are, connected with one another via the data bus, CAN (Controller Area Network) and communicate the necessary signals via the two cables, CAN-High and CAN-Low.
Technically the latest control modules of the trailer hitches could hook up into the CAN-Bus and communicate digitally with the onboard control units, but this is seldom the case.

Check controll for the electrical kit – what is it and how does it work?

25. April 2018 um 12:17

check controllThe term check controll is omnipresent, especially when it comes to the electronics of a car. But what does the term stand for and what does it mean? The surveillance of the lamps and their proper functioning is labelled as check controll system, the system is part of the vehicle’s on-board electronics. It serves as a controlling mechanism of different vehicle’s functions, part of those are the full beam, stop lights and rear fog-lamps. If these lights and lamps fail, the driver is informed due to the systems optical indications. Hence, the indications can also be digital informations of the board computer.

What must be payed attention to concerning vehicles‘ check controll?

A vehicle’s electronics are not only complicated but also finely calibrated, therefore, even small interventions can have a huge impact. For vehicle’s which entail check controll the electrical kit must hence be conceptualized in a way that ensures the tap of the lighting functions before the lamp test device takes place.

A different solution is to use an electrical kit with a special trailer control device, where lamp currents are generated for the trailer from the vehicle battery out. Incidentally, such a cable set is also strongly recommended for vehicles with too small cable cross-sections (<0.752). We already pay close attention to this when designing and developing our electrical kits. So you just have to make sure when buying that the electrical kit is suitable for vehicles with check-control.

Electric kits with trailer control unit MVG-type 4112

Our electric kits, which are fitted with a trailer control unit of the MVG-Type 4112, are ideally suited for vehicles with check-control and / or with insufficient cable cross-sections (<0.752). You also benefit from the following product advantages:

  • Short-circuit proof outputs of the trailer lighting functions
  • Suitable for both LED and incandescent trailers
  • Microprocessor controlled
  • Monitoring of the charging line / charging active with the engine running and a light function
  • Made in Germany