Component description for trailer recognition control unit - GF31.19-P-4050FQ
MODEL 218.9 with CODE 550 (Trailer coupling)
Location
The trailer recognition control unit is located in the trunk behind the right luggage compartment lining.
Task
The trailer recognition control unit has the following tasks:
- Reading in of sensors, pickups and signals
- Evaluation of input factors
- Monitoring of ball neck lock
- Trailer recognition
- Trailer consumer actuation
- Lamp failure indicator
- Emergency light function
- Consumer shutoff
Reading in of sensors, pickups and signals
The input factors are read in via the following connections:
- Direct line
- Interior CAN (CAN B)
Direct line
The signals from the following components are read via direct lines:
- Unlocking trailer hitch (A63)
- Trailer hitch lock switch (S142)
Interior CAN
The signals are read in by the trailer recognition control unit via the interior CAN.
The functions that use these signals are described in the individual function descriptions (see block diagram or function schematic).
Evaluation of input factors
The input factors are evaluated by the microprocessor and the corresponding components are actuated.
Monitoring of ball neck lock
The trailer recognition control unit monitors the correct seating of the mechanically-hinged ball neck. To this end, the status of the trailer hitch lock switch is read-in directly. If the ball neck is not in the correct position, this is indicated by a flashing LED in the trailer hitch unlocking device (on the left inside the luggage compartment). At circuit 15 ON a corresponding signal is also sent over the interior CAN to the instrument cluster (A1). A warning message appears in the multifunction display (A1p13) of the instrument cluster.
Trailer recognition
By means of current monitoring of the "left turn signal" and "brake lights" outputs the trailer recognition control unit detects whether the supply line of the trailer is plugged in or not. When one of the two loads is recognized, the trailer is deemed to be recognized. This status is sent to the interior CAN.
Actuation of the trailer lighting
The trailer recognition control unit actuates the following trailer components over the trailer socket (X58):
- Brake lights, flashing brake lights
- Rear fog lamp
- Backup lamp
- Turn signal lamp
- Taillights and license plate lamp
- Trailer power supply, circuit 30g
If the flashing brake lights are requested, the front SAM control unit with fuse and relay module (N10/1) sends the time for which the brake lights are to remain dark. The trailer recognition control unit cancels brake light actuation for the duration of this time.
Lamp failure indicator
The trailer recognition control unit monitors the function of the trailer lamps. However, only faults in the general lamp path are recognized. If a failure is detected a corresponding signal is transmitted on the interior CAN.
Trailer lighting in LED version:
The minimum current for each lamp path must be I = 50 mA for reliable lamp failure detection. When this minimum current is undershot, a fault message appears in the multifunction display of the instrument cluster although the trailer lighting is functioning correctly (only with LED turn signals lights).
Emergency light function
If the trailer recognition control unit fails or if there is a corresponding request placed via the interior CAN, the trailer's taillights are actuated.
Consumer shutoff
If a corresponding request is issued by the rear SAM control unit with fuse and relay module (N10/2), circuit 30 to the trailer socket will be switched off. The lighting system of the trailer is not actuated.
| Trailer recognition control unit wiring diagram | PE31.19-P-2101-97XAA |