Component Description For Trailer Recognition Control Unit - GF31.19-P-4050FH
Model 238
Up To Model Year 2021
With Code 550 (Trailer coupling)
Shown On Model 238.3
Shown On Model 238.4
Location
The trailer recognition control unit is in the trunk recess under the cover.
Tasks
The trailer recognition control unit has the following tasks:
- Reading in of sensors and signals
- Evaluation of input factors
- Release, swivel and lock trailer hitch
- Monitoring of ball neck lock
- Trailer recognition
- Trailer consumer actuation
- Lamp failure indicator
- Emergency light function
- Consumer shutoff
Reading in of sensors 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 a direct line:
- Trailer hitch release switch (S62/24)
- Hall sensor in trailer hitch release (A63)
- Locking finger sensor in trailer hitch release
Interior CAN
The signals are read in by the trailer recognition control unit via the interior CAN.
Evaluation of input factors
The input factors are evaluated by the microprocessor and the corresponding components are actuated.
Release, swivel and lock trailer hitch
The ball neck of the trailer hitch can be swiveled in and out together with the trailer socket (X58). When in the swiveled-in or swiveled-out position, the ball neck is released by operating the trailer hitch release switch. Swiveling and locking are both performed manually.
The trailer recognition control unit detects the position of the ball neck at any given time using a Hall sensor located in the trailer hitch release.
The following components are integrated into the trailer hitch release:
- Hall sensor for detecting position of ball neck
- Motor for opening ball neck lock
- Locking finger for ball neck lock
- Locking finger sensor for monitoring the ball neck lock
Monitoring of ball neck lock
The trailer recognition control unit monitors the correct seating of the ball neck. To this end, the status of the locking finger sensor in the trailer hitch release is read in directly. A ball neck that is not in a correct position is indicated by an LED in the trailer hitch release switch flashing on and off. At circuit 15 ON a corresponding signal is also sent via interior CAN, electronic ignition lock control unit (N73) and the user interface CAN (CAN HMI) to the instrument cluster (A1). A warning message appears in the instrument cluster.
Trailer recognition
The trailer recognition control unit monitors the current of the "left turn signal" and "brake lights" output, to determine whether trailer hitch supply line is plugged in or not. When one of the two loads is recognized, the trailer is deemed to be recognized. This status is sent via the interior CAN.
Trailer consumer actuation
The trailer recognition control unit actuates the following trailer components via the trailer socket:
- Brake light
- Rear fog lamp
- Backup lamp
- Turn signal lamp
- Taillight and license plate lamp
Lamp failure indicator
The trailer recognition control unit monitors the function of the light sources on the trailer. However, only faults in the complete path are detected. If a failure is detected, a corresponding signal is sent over the interior CAN.
LED version trailer lighting: The minimum current for each lamp path must be I = 50 mA for reliable lamp failure detection. If this minimum current is not reached, a fault message appears in the instrument cluster even if the trailer lighting is functioning correctly.
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 requested by the rear SAM control unit (N10/8), circuit 30 to the trailer socket is switched off. The lighting system of the trailer is not actuated.
| Trailer recognition control unit wiring diagram | PE31.19-P-2101-97DCA |