Trailer Detection (PDC Park Distance Control)

Trailer module and trailer coupling release, functional description
This functional description describes the trailer module 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)

The following are also described:
- The control module for the trailer coupling release in the E9x with the associated electrical folding trailer coupling and
- The control module for the trailer coupling release in the E6x with the associated fully automatic trailer coupling

This equipment range is fitted with the optional extra 3AC "trailer coupling with electrical articulated ball end" in these vehicles.
For a more detailed description of the trailer coupling releases, see: SBT 61 08 04 120.

The trailer module is an auxiliary control module for the footwell module (E8x, E9x, E7x, R5x) or light module (E6x). At the moment, two different trailer modules are installed. The AHM3 is the version that was deployed up to 09/2006. The AHM3+ is the revised version. Essentially, it differs from the AHM3 with regard to the following characteristics:
- 2 lines and fuses for the power supply, enabling more electrical power output to be provided for the trailer lighting.

The trailer module separates the current circuits of the trailer from the circuit of the towing vehicle. The control module also reports the status of the articulated ball head to the trailer module for the trailer coupling release. These states are: Trailer coupling locked or not locked.

The AHM3+ will be fitted as volume production launch on the E70 and R55. In all the other model series mentioned above, the AHM3+ will be fitted as of 09 / 06.
Observe the following differences with regard to fitting and the function of the trailer module as well as the trailer coupling:
- MINI
The trailer module will be fitted in the R56 version as optional equipment and accessories. The trailer module delivers the electrical energy for the rear bicycle rack offered as optional equipment and accessories. A trailer coupling is not offered for the R56. A detachable trailer coupling is fitted in the R55.
- BMW
The trailer module is fitted if the vehicle is equipped with a trailer coupling. The trailer coupling can be firmly installed or removable. Moreover, it is also possible to fit a semi-electric or fully electrical articulated ball head.

Brief description of components
Alongside a microprocessor, the trailer module consists essentially of overload-resistant sense FET power circuit breakers for the trailer power circuits.

The sense outputs of the power circuit breakers enable monitoring of the power circuits for excess current or wire breaks. The power circuit breakers are activated via CAN messages.

Also implemented is an input for direct activation of the brake light by the brake light power circuit of the towing vehicle (hard-wired). The emergency function guarantees the function of the brake light on failure of the CAN bus.

The following control modules are involved in the functions of the trailer module:
- AHM trailer module
The trailer module controls and monitors the current circuits of the trailer. The trailer module also separates the current circuits of the trailer from the vehicle network of the towing vehicle. In the event of system faults, the trailer module creates the Check Control messages.
- Control module for the electric folding trailer coupling (E9x)
The control module is connected to the vehicle network by a 16-pin connector. The control module has no direct connection to the bus system. The electrical folding trailer coupling release is operated using a button in the luggage compartment. The control module is installed in the luggage compartment in the device carrier. The control module is neither programmable nor self-diagnosable.
- Control module for the fully automatic trailer coupling (E6x)
The control module is connected to the vehicle network by a 16-pin connector and a 4-pin connector. The control module has no direct connection to the bus system. The fully automatic trailer is operated using a button in the luggage compartment. The control module is installed in the luggage compartment in the carrier or in the luggage compartment recess. The control module is neither programmable nor self-diagnosable.
- CAS: Car Access System
The CAS control module delivers the signal for terminal 15. This signal is connected at the control module of the trailer coupling release.
- JBE: junction box electronics
The junction box supplies the trailer module with voltage (terminal 30g). Moreover, the junction box also supplies the control module of the trailer coupling release with voltage.

The trailer module detects overvoltage and undervoltage in the vehicle network. Outside the valid range of 9 to 15 Volt, functions that are not relevant to safety are switched off. For example, the trailer coupling release cannot be activated with undervoltage or overvoltage.

Index:

System functions
The following functions are described:
- Trailer lighting
- Trailer detection
- Trailer coupling release

Trailer lighting
The trailer lighting runs the following functions:
- Brake light
- Parking light / parking lamp
- Indicating, hazard warning lights, crash alarm hazard warning lights, DWA alarm flashing
- Rear fog light
- Reversing lights
The trailer module activates the individual lamp electrical circuits of the trailer. The implemented functions for the trailer lighting are described in the following section.
- Brake light
The brake light on the trailer is switched on when the service brake in the towing vehicle is operated.
- Parking light / parking lamp
The parking light on the trailer is activated when the light switch on the towing vehicle is in the 'parking light' or 'low beam' position. When the Automatic Light Control is activated, the parking light of the trailer is switched on depending on the level of brightness.
- Indicating, hazard warning lights, crash alarm hazard warning lights, DWA alarm flashing
For turn indicating, there are two indicating functions implemented by the trailer module.
- One-touch indicating: When the indicator / high-beam switch is touched briefly, the turn-indicator lights are activated briefly. The number of flashing pulses here depends on the encoding of the towing vehicle.
- Continuous flashing: When the indicator / high-beam switch is 'overpressed' beyond the resistance point, the turn-indicator lights are activated with the function "continuous flashing".
The flash frequency is adapted to the flash frequency of the towing vehicle by the trailer module. At the start of each flashing period, CAN messages are sent in cycles. These messages serve to synchronize the flash frequency between the towing vehicle and trailer. If a turn-indicator light on the vehicle or trailer is defective, the flash frequency is doubled (defective flashing).
- Rear fog lamp:
The rear fog lamp is switched on with
- terminal 15 On and
- the light switch of the towing vehicle in the low beam position
- the rear fog lamp activated by the switch.
or with
- terminal 15 On and
- the light switch of the towing vehicle in 'parking light' position and
- the fog lights activated and
- the rear fog lamp activated by the switch.
The rear fog lamp is switched off again when
- the rear fog lamp is deactivated by the switch
- terminal 15 OFF, or
- light switch OFF.
- Reversing light
The reversing light is switched on when reverse gear is engaged on the towing vehicle and terminal 15 is ON. The reversing lights are switched on with a delay of a fraction of a second to avoid their flashing during gear changes.

Trailer detection
The trailer module detects a trailer as connected when at least two loads (cold measurement) are detected at the lighting outputs. The trailer module then reports the status "Trailer connected". This status report is implemented in the towing vehicle in a number of control modules. For example, the Park Distance Control is disabled at the rear.
In vehicles built up to 2006, the reversing light and rear fog light of the towing vehicle are disabled for trailer towing.
In vehicles built after 2006, the reversing light is no longer disabled. If the rear fog light on the trailer fails, there is a switch to the rear fog light of the towing vehicle.

Electrical folding trailer coupling
The electrical folding trailer coupling is a component of the optional extra 'trailer coupling with articulated ball head'. This optional extra has been offered for the E9x since 03/2007. The electrical folding trailer coupling is operated using a button in the luggage compartment.

Fully automatic trailer coupling
The fully automatic trailer coupling is a component of the optional extra 'trailer coupling with articulated ball head'. This optional extra has been offered for the E6x since 03/2007. The fully electric trailer coupling is operated using a button in the luggage compartment.

Index:

There is a two-colour LED for the indicator lamp in the button. The following signals are possible:
- The LED lights up green:
the trailer coupling is in the locked end position.
- The LED flashes slowly red (2 Hz):
the trailer coupling is not in the locked end position.
- The LED flashes quickly red (4 Hz):
The drive has been activated for longer than 4 seconds.
The current necessary for the release function drive has not been reached (12 Amperes).
The drive for the trailer coupling release is attached to the release unit. The ball head can only be released if the following conditions have been met:
- Terminal 15 OFF
- Trunk lid open
The trailer coupling can be operated as of terminal 30g ON. The following signal states must be present:
- Terminal 30g: high signal
- Button for trailer coupling release: low signal
- Terminal 15: low signal
- Luggage compartment contact switch: low signal
- Micro-switch of trailer coupling release, output 1: low signal
- Micro-switch of trailer coupling release, output 2: high signal
After a successful check of the signal states, the DC motor for the trailer coupling release is activated.

Index:

The drive for the trailer coupling release consists of a direct current motor and a reduction gear. The following components are integrated in the release unit:
- Micro-switch with slide and compression spring
- Drive disk for the micro-switch
- Drive disk for the release lever
- Release lever

Index:

Notes for Service department
Diagnosis instructions for the trailer module
The trailer module detects and reacts to the following faults:
- Checksum fault of the various memories and watchdog reset
- Faults of the CAN drivers
- Wire faults of the CAN interface and of the brake light input
- Wire fault of all outputs with short circuit and wire break
- Undervoltage / overvoltage and implausibility of the control module voltage in comparison with the on-board supply voltage
- Implausibility of a CAN message �Braking� compared to the hard-wired brake light input at the control module
- Implausibility of the sense values of the lighting outputs of the control module
- Faults on the lamp outputs of the trailer module are output as Check Control messages

Notes on trailer coupling release
For a more detailed description of the trailer coupling release, see: SBT 610804120.

Notes on encoding / programming
After installation of a trailer module, the control module must be re-encoded. In doing so, observe the various national versions.

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