Currently known fault profiles of the trailer module

The functional description describes currently known fault profiles of the trailer module and trailer interlock for the following vehicles:

E81, E87, E90, E91, E92, E93 (BMW 1 Series, 3 Series)
E60, E61, E63, E64 (BMW 5 Series, 6 Series)
E65, E66, E67, E68 (BMW 7 Series)
E70 (BMW X5)
R55, R56 (MINI)

These fault profiles can occur on all vehicles and are sorted below into fault profiles of the electrical swing-out and electrical release trailer coupling. These fault profiles are not registered by the self-diagnosis of the control unit. The fault profiles are symptom-based and intended as supplementary information for the present diagnosis.

Known fault profiles for the electrical swing-out trailer coupling

Electrical swing-out trailer coupling without function

Description
The customer complains that the trailer coupling release is not functioning. The trailer coupling cannot be released electrically and does not swing out. The fault code 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.	Description	No.	Description
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.	Description	No.	Description
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 profile 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 micro-switch 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 actuation. A short-circuit caused by water entry can be the cause of this fault.

No.	Description	No.	Description
1	Traces of corrosion on the motor of the electrical swing-out trailer coupling	2	Traces of corrosion on the base of the drive mechanism housing

Known fault profiles for the electrical release trailer coupling

The release of electrical release trailer coupling causes it to swing directly into the outward articulated end position
- Description
  The customer determines that the trailer coupling is released by pressing the unlock button and then locks in place directly in the articulated outwards end position. The specified released intermediate position is swung over.
- Cause
  The cause of this behaviour is related to the manufacture. On swinging out, the ball end is braked by a rubber mat with a defined torque. The manufacturing tolerance mean that this braking torque can be too low. This enables the complete swing-out to the end position. At the moment, there is no remedial measure, as the braking torque is set at the manufacturer and cannot be changed in Service (permanent bonding).

No liability can be accepted for printing or other errors. Subject to changes of a technical nature