Component Description For Trailer Recognition Control Unit - GF31.19-P-4050RF
Model 205, 253 with code 550 (Trailer coupling)
Shown on model 205.0 up to 31.05.2018
Location
The trailer recognition control unit is located in the trunk in the spare wheel well.
Tasks
The trailer recognition control unit has the following tasks:
- Reading in of 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 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:
- Trailer hitch release (A63) (model 205)
- Fully electric trailer hitch swivel unit (A63/2) (model 253)
- Trailer hitch release switch (S62/24) (model 205)
- Trailer hitch switch (S142/2) (model 253)
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 the appropriate block diagram or function schematic).
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) using the electromechanical swivel unit. This is done by actuating the trailer hitch release switch (model 205) or the trailer hitch switch (model 253).
By means of a LED in the trailer hitch release switch (model 205) or in the trailer hitch switch (model 253), the different statuses of the trailer hitch ball neck are signaled as follows:
- The LED is OFF in the rest position.
- The LED flashes during the swiveling process.
- In the operation item, the LED lights up permanently (model 205 as of 01.06.2018, model 253 as of 01.06.2019) or is off (model 205 up to 31.05.2018, model 253 up to 31.05.2019).
A fault message is displayed in the multifunction display (A1p13) of the instrument cluster (A1) if the swiveling process cannot be initiated because one of the following conditions are not fulfilled:
- Selector lever in "P" position (park pawl) (transmission 722, 724, 725)
- Gearshift lever in "N" position (transmission 716)
By evaluating the signals from a Hall sensor in the electromechanical swivel unit, the trailer recognition control unit detects the current position of the ball neck.
The following components are integrated in the electromechanical swivel unit:
- Hall sensor for detecting position of ball neck
- Swivel motor for swiveling ball neck in and out
- 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 electromechanically swiveling ball neck. For this purpose, the trailer recognition control unit evaluates the signals from the locking finger sensor in the electromechanical swivel unit. If the ball neck is not in a correct position, the trailer recognition control unit transmits - for circuit 15 ON - a relevant signal via the interior CAN, electronic ignition lock control unit (N73) and user interface CAN (CAN HMI) to the instrument cluster. A corresponding warning message then appears in the instrument cluster multifunction display.
Trailer recognition
By means of current monitoring of the "left turn signal light" 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. The trailer recognition control unit sends the trailer recognition status 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. Only faults in the entire path are detected however. If a failure is detected, the trailer recognition control unit sends corresponding information via the interior CAN.
LED trailer lighting version: The minimum current for reliable lamp failure recognition for each lamp path is 50 mA. When this minimum current is dropped below the limit, a fault message appears in the multifunction display of the instrument cluster although the function of the trailer lighting is OK.
Emergency light function
If the trailer recognition control unit fails or if there is a corresponding request via the interior CAN, the taillights on the trailer are actuated via the trailer socket.
Consumer shutoff
Model 205 up to 31.05.2018, model 253 up to 31.05.2019:
If requested by the rear SAM control unit (N10/8), circuit 30g to the trailer socket is switched off. The lighting system of the trailer is not actuated.
Model 205 as of 01.06.2018, model 253 as of 01.06.2019:
If a corresponding request is issued by the front SAM control unit (N10/6) circuit 30t to the trailer socket is switched off. The lighting system of the trailer is not actuated.
| Trailer recognition control unit wiring diagram | Model 253 as of model year 2020 with code 550 (Trailer coupling) | PE31.19-P-2101-97FCA | |
| Model 205 as of model year 2019 with code 550 (Trailer coupling) | PE31.19-P-2101-97FBB | ||
| Model 205 up to model year 2019 with code 550 (Trailer coupling) Model 253 up to model year 2020 with code 550 (Trailer coupling) | PE31.19-P-2101-97FBA |