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CAN data bus technology (also called CAN bus technology: Controller Area Network) is a special type of data transmission in cars. It forms the backbone of the electronic network as a compact, central data distributor in modern cars and connects the majority of car control units with each other, exchanging data and transmitting signals to activate functions.

Today a modern car contains up to 70 different electronic control units that exchange messages with each other  providing various utilities.

Using coventional wiring, the number of lines, plug connections and fuse boxes necessary for this package would be unmanageable. Production processes would be lengthy and sources of errors would be difficult to determine.  CAN data bus technology provides the perfect electronic solution for this problem.

For some vehicles, the trailer control unit is also connected to the on-board network of the car using CAN data bus technology.

CFC® stands for CAN frequency control – an electronic installation kit from JAEGER automotive for trailer control and functional monitoring of the future. It was developed for modern vehicles that are fitted with CAN data bus technology.

If your car has digital data bus technology and you want to fit a tow-bar to it, you can install the JAEGER automotive CFC® electronic installation kit in a few work steps.

The intelligent CFC® trailer module has got a microprocessor in the CFC® electronic installation kit. This trailer module comunicates  with the CANetwork in your car and optimises it for new tasks.

All lighting functions of the trailer are controlled by the Body Controller and conveniently monitored.

The AFC / CFC® module requires a 12 Volts constant positive connection to operate the electronic control module. Indicator and trailer lighting would malfunction without this power supply.

A constant 12 volts positive connection is absolutely necessary to energize hazard  and parking lights in case of breakdown.

The trailer socket can not be fully controlled with a trailer test device with LED technology as the trailer control modules send out a test current for detecting the trailer.  Please use a light bar with genuine 21 Watt lamp load, a trailer or a bike carrier for correct control.

Modern trailer modules communicate with the control units of the vehicle. Comfort functions such as lamp failure notification, parking assistant switch off, stabilisation and fog light shut down only operate when the drawing vehicle has“learned” that a tow-bar is installed. For this reason, it is necessary for the vehicle to be coded  for trailer towing purposes utilising preferably manufacturers genuine diagnostic testers.

CAN data bus technology (also called CAN bus technology: Controller Area Network) is a special type of data transmission in cars. It forms the backbone of the electronic network as a compact, central data distributor in modern cars and connects the majority of car control units with each other, exchanging data and transmitting signals to activate functions.

Today a modern car contains up to 70 different electronic control units that exchange messages with each other  providing various utilities.

Using coventional wiring, the number of lines, plug connections and fuse boxes necessary for this package would be unmanageable. Production processes would be lengthy and sources of errors would be difficult to determine.  CAN data bus technology provides the perfect electronic solution for this problem. 

For some vehicles, the trailer control unit is also connected to the on-board network of the car using CAN data bus technology.

The ground pole of the battery was probably not disconnected as prescribed in thefitting instruction. The control module can then not register on the vehicle system.
For a reset of the module see Troubleshooting CFC®-PDF.

Lexicon - JAEGER automotive is glad to help you

The lexicon covers all important terms regarding our range of products. The entries are listed alphabetically. You can find an article of your interest using the search function. All entries can also be  found using the alphabetical index.

AFC (Automatic Frequency Control)
AFC technology is a trailer indicator monitoring system with integrated control unit. It ensures the legally prescribed monitoring of the trailer indicator lights without additional optical (C2 control lights) or acoustic control equipment (e.g. buzzer).


The function that monitors the indicator lights on the drawing vehicle is adopted for the trailer. This means: If a light on the drawing vehicle fails, the control light installed on the dashboard flashes twice as fast as an intact indicator light. The same principle applies when an indicator light fails on the trailer attached. The control lights on the dashboard respond with a doubled flash frequency.
The AFC control unit requires a steady current supply to function (terminal 30, battery plus).
AFC technology has many advantages:
  • The control unit is installed independently of the original  indicator relay provided in the vehicle. This is why AFC technology can be installed in many types of vehicles.
  • AFC technology is very suitable for vehicle-specific and universal electrical kits.
  • No installation work is required on the dashboard or central electrical system.
  • No uninstallation or installation of the steering wheel (airbag) and/or combo instrument.
  • No need to find a suitable installation location for the C2 control light.
  • The appearance of the dashboard is not changed as no C2 control light or switch panel has to be installed in the trim.
  • The electrical kit is often only  connected in the rear of the vehicle.
  • Vehicle-specific electrical kits with AFC technology are always easy to install.
  • Installing an AFC electrical kit saves considerable installation work and time when compared to a conventional electrical kit. This more than compensates for the additional price.
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