Known fault patterns for the electrical swing-out trailer coupling
- The trailer tow hitch is inoperative, a Check Control fault message (trailer tow hitch not locked) occasionally appears while driving. Affected vehicles: E90 and E91 .
- Description
The customer complains that the electrical swing-out trailer tow hitch is inoperative.
- Cause
Water ingress in the control unit for unlocking the trailer tow hitch, caused by obstructions in the panorama glass roof water drain hose, leaks in the fuel filler flap lock, Touring side window, for example.
- Electrical swing-out trailer coupling without function
- Description
The customer complains that the electrical swing-out trailer tow hitch is inoperative. The trailer coupling cannot be released electrically and does not swing out. The fault memory contains no fault for the trailer coupling release. However, other faults can be stored. The indicator light in the button for the trailer coupling release flashes slowly red (2 Hz).
| No. | Designation |
|---|---|
| 1 | Cable entry point in the drive mechanism with wire harness pulled out |
| 2 | Rubber seal between base and cover of the drive mechanism |
| 3 | Housing of the drive mechanism |
| No. | Designation |
|---|---|
| 1 | Opened drive mechanism of a defective electrical swing-out trailer coupling |
| 2 | Micro-switch in the drive mechanism |
- Cause
A possible cause for this fault pattern can be that water has entered through a faulty (squashed) sealing ring into the drive mechanism of the trailer coupling. Water can also enter the drive mechanism at the cable entry point
Another cause can be a failure of the micro-switch. This micro-switch detects the end position of the ball end. If this microswitch is defective, the trailer module does not detect the position of the ball end. The ball end can then only be swung out with emergency activation. A short circuit caused by water entry can be the cause of this fault.
| No. | Designation |
|---|---|
| 1 | Traces of corrosion on the electric motor of the electrical swing-out trailer tow hitch |
| 2 | Traces of corrosion on the base of the drive mechanism housing |