Function of the CFC9
The CFC9 trailer module electrically connects a trailer to a towing vehicle and is used for vehicles with a CAN bus
system (Controller Area Network).
The CAN bus interface is used to control the relevant lighting functions on the trailer.
The CFC trailer module can control and monitor both bulb and LED rear lights on trailers.
If a fault is detected in the trailer lights, the driver is alerted visually and/or audibly.
In addition, if a fault is detected in the direction indicator, the indicator function is replaced by the corresponding
parking light on the affected side (light substitution), so that the following vehicle can detect a change of direction
even if the direction indicator is faulty.
Identification of the module
The module and thus the module number are identified via the sticker on the module's connector holder
Module connector pin assignment
| 1 | CAN GND | CAN Ground |
| 2 | CAN-H | CAN-Bus High |
| 3 | CAN-L | Lowspeed CAN-Bus |
| 4 | LIN | LIN |
| 5 | REF IO1 | Reference IO1 |
| 6 | IO1 | Input / Output 1 |
| 7 | 54 | Brake light tap |
| 8 | REF IO2 | Reference IO2 |
| 9 | IO2 | Input / Output 2 |
| 10 | 54 ANH | Brake light trailer |
| 11 | NC | Not connected |
| 12 | BLL ANH | Indicator left trailer |
| 13 | 58L ANH | Parking light left trailer |
| 14 | 31 | Ground (Battery minus) |
| 15 | 30L | Power supply (Battery plus) |
| 16 | BLR ANH | Indicator right trailer |
| 17 | 30R | Power supply (battery plus) |
| 18 | NSL ANH | Rear fog light trailer |
| 19 | RFL ANH | Reversing light trailer |
| 20 | NSL FZG IN | Input Cutoff rear fog light vehicle |
| 21 | 58R ANH | Parking light right trailer |
| 22 | NSL FZG IN (NSL ANH) | Output rear fog light trailer for rear fog light cutoff |
| 23 | NSL FZG OUT | Output Cutoff rear fog light vehicle |
| 24 | VC IN | Input Voltage Control |
| 25 | VC OUT | Output Voltage Control |
LED - Status
Installation OK
No trailer connected
Installation OK
Trailer connected
No communication with the vehicle
Low battery voltage or blown fuse
CAN-H or CAN-L not connected
CAN-H and CAN-L interchanged
Short circuited charging line (VC)
Short-circuited light channels
(54 / 58/ BLL / BLR / NSL / RFL)
Diagnostic measurements
General information
The following conditions apply to all measurements listed:
- Ignition ON
- Module disconnected
The use of a calibrated multimeter or voltmeter is recommended for reliable measurement
Module power supply (B/+30)
There are 2 power supplies for the module. In order to create a correct diagnosis, both must be tested
- Set multimeter to voltage measurement
- Measure with the negative measuring tip on a clean ground connection on the vehicle
- Measure from pin 15 (or Pin 17) on the control unit to vehicle ground
- The multimeter should display a voltage of approximately 12 Volt
- If 12 V is not reached, the battery voltage, the fuses and the cable itself must be checked
Module grounding (GND/31)
- Set multimeter to voltage measurement
- Measure with the negative measuring tip on pin 14
- Measure with the positive measuring tip on pin 17
- The multimeter should display a voltage of approximately 12 Volt
- If no voltage of approximately 12V is displayed, the groundling line from the module to the vehicle must be checked
CAN BUS Measurement
The so-called CAN high voltage is present on one line and the CAN low voltage on the other
The so-called high-speed and low-speed CAN bus systems exist independently of this. These differ in the general voltage
Both systems have a high voltage and a low voltage, but do not have the same voltage ranges:
Highspeed CAN-Bus
High approx. 2.6V
Low approx. 2.3V
Lowspeed CAN-Bus
High approx. 0.5V
Low approx. 4.5V
CAN-Bus High
- Set multimeter to voltage measurement
- Measure with the negative measuring tip on a clean ground connection on the vehicle
- Measure with the positive measuring tip on pin 2
- The multimeter should now display one of the two voltages, depending on the CAN type:
Highspeed: approx. 2.6V / Lowspeed approx. 0.5V - If these voltages are not displayed, the tapping of the CAN bus lines must be checked. (Incorrectly connected, contact fault, etc)
Make sure that the ignition is switched off before you disconnect or connect the CAN-Bus cables
CAN-Bus Low
- Set multimeter to voltage measurement
- Measure with the negative measuring tip on a clean ground connection on the vehicle
- Measure with the positive measuring tip on pin 3
- The multimeter should now display one of the two voltages, depending on the CAN type:
Highspeed: approx. 2.3V / Lowspeed approx. 4.5V - If these voltages are not displayed, the tapping of the CAN bus lines must be checked. (Incorrectly connected, contact fault, etc)
Make sure that the ignition is switched off before you disconnect or connect the CAN-Bus cables
Support contacts
Do you need more information?
Contact your country-specific sales partner
