Trailer Connection Unit [AAG] Control Unit, Component Description - GF31.19-D-4200HU
MODEL 906.153/155/633/635/637/653/655/657/733/735 with CODE (E40) Trailer socket (7-pin)
Location
The trailer connection unit [AAG] control unit is located in the driver seat frame.
Task
General
The trailer connection unit [AAG] control unit routes the signals of the exterior lights (ABL) system to the trailer socket 7-pin (X58) and to the brake booster connector (X175) and reports back any change in status.
The following trailer lamps are monitored by the trailer connection unit [AAG] control unit (up to 31.08.2007):
- Turn signal/brake lamp:
- In the event of any bulb failure, entry in fault memory, Controller Area Network (CAN) information to instrument cluster (A1) and doubled-up flasher frequency
- Taillamp:
- Bulb failure is not recognized until both lamps fail
The reversing lamp is not monitored.
The fault entry in the trailer connection unit [AAG] control unit is removed in the event of a bulb failure in the brake/turn signal lamp after a status change "circuit 15R ON/OFF".
Input and output signals
- CAN input signals
- CAN output signals
- Direct input signals
- Direct output signals
CAN input signals
The trailer connection unit [AAG] control unit is an interior CAN (CAN B) user and, e.g. receives the following signals:
- "U_BATT (battery voltage)" from EZS control unit (N73)
- "KM_KI (kilometer reading)" from instrument cluster
- "LIGHT_ST (status of exterior lights or rotary light switch (S1))" from SAM control unit (N10)
CAN output signals
The trailer connection unit [AAG] control unit sends the following CAN signals:
- "ANH_ERK (trailer operation detected)" to the EZS control unit
- "BEL_ANH_ST1 (status of trailer lighting)" to the instrument cluster
- "BEL_ANH_ST2 (status of trailer lighting)" to the SAM control unit
- "ANH_ERK (trailer operation detected)" to the PTS control unit (N62), with code (EZ8) Parktronic system (PTS)
Direct input signals
The trailer connection unit [AAG] control unit receives the following input signals directly:
- Circuit 30
- Circuit 31
- Right taillight or turn signal lights (trailer recognition)
Direct output signals
Trailer socket (7-pin)
Brake booster connector
Trailer socket (7-pin)
The following signals are sent directly to the trailer socket 7-pin:
- Left turn signal/brake lamp
- Right turn signal/brake lamp
- Left taillight (for left and right taillight on trailer)
- Backup lamp
The flashing and braking function are assigned to one lamp. The signals for flashing and braking are each sent to the corresponding lamp. Actuation is as an "XOR" logic operation.
Brake booster connector
The following direct signal is sent to the brake booster connector:
- Stop lamp error messages in instrument cluster
The brake booster is used to actuate trailers with electrical drum brake and it can be retrofitted in Service workshops.
| Error message for trailer connection unit [AAG] control unit | Display (with code (JK3) High-end instrument cluster standard with speedometer in km) | Display (without code (JK3) High-end instrument cluster standard with speedometer in km) |
|---|---|---|
| Brake defective: Brake booster fault | The brake fluid level warning lamp (A1e21) goes on | The brake fluid level warning lamp goes on |
| Brake defective: Trailer connection unit [AAG] control unit - Timeout | The brake fluid level warning lamp goes on | The brake fluid level warning lamp goes on |
| Brake light defective (up to 31.8.2007): Brake light defective | "Trailer brake lamp" shown on display (A1p1) | Bulb failure indicator lamp (A1e1) goes on |
| Brake light defective (up to 31.8.2007): Trailer connection unit [AAG] control unit - Timeout | "Trailer electronics" appears in display | Bulb failure indicator lamp goes on |