Monitoring of terminal 15 and Check Control message

• E60, E61

The CAS transmits a status signal for terminal 15 to the control unit for the electrically pivoted trailer coupling. The control unit transmits the status signal and the operating statuses of the trailer coupling to the trailer module (AHM).

The CAS also transmits the status signal for terminal 15 to the trailer module via the K CAN. The plausibility of both signals is checked in the trailer module.

Signals from the control unit for the electrically pivoted trailer coupling to the AHM:

• Status signal of terminal 15 OFF: low signal
• Status signal of terminal 15 ON and pivoting ball head in limit position: PWM signal (pulse-width-modulated signal) 450 ms low -> 50 ms high -> 450 ms low -> etc.
• Status signal of terminal 15 ON and ball head pivoting or halted in intermediate position: high signal

The trailer module generates a Check Control message. The Check Control message is sent via the K CAN. The Check Control message is only indicated after the engine is restarted by a Check Control symbol (red) in the instrument cluster and by an acoustic signal of limited duration (E90 up to 09/2005: continuous signal).

Check Control message:

• Trailer coupling locked

  or

• Trailer coupling electronics

Further information is provided in the Central Information Display (CID).

• E90, E91, E92, E93 

Terminal 15 is monitored by a live signal as follows:

• Terminal 15 ON and trailer coupling locked:

The trailer coupling release control unit transmits the live signal to the trailer module (AHM). To do this, the control unit activates the output to the AHM every 450 ms.

The trailer module detects a system error by the absence of the live signal.

• E90 up to 09/2005 

A yellow Check Control symbol in the instrument cluster indicates the Check Control message: Vehicle on lifting platform. The loudspeaker simultaneously emits a continuous signal.

If the trailer coupling is released with terminal 15 ON, a Check Control message is likewise generated. The loudspeaker is switched on for 30 seconds.

The output to the AHM has a high resistance when terminal 15 is OFF.

• E90/E91 from 09/2005 and E92, E93: 

From 09/2005, a separate, unambiguous Check Control symbol has been provided for the trailer coupling release.