AHM: Trailer module

Depending on the series and trailer tow hitch version, the trailer module (AHM) is supplied with voltage via terminal 30F and terminal 30B. The voltage regulator that is supplied redundantly via terminal 30F supplies the microcontroller in the trailer module (AHM) with a voltage of 5 volts.

The cyclical voltage measurement evaluates the two power supplies (terminal 30F). If both power supplies are within the valid voltage range, the trailer module (AHM) makes all the functions available.

The microcontroller monitors the trailer power circuits via the switch outputs of the semiconductor switches.

In the event of system faults, the trailer module (AHM) creates the Check Control messages. The trailer module (AHM) detects overvoltage and undervoltage in the vehicle electrical system. Outside the valid range of 9 to 15 Volt, functions that are not relevant to safety are switched off.

If a voltage supply fails, the lighting function for the trailer lighting is restricted. In emergency operation only certain load circuits remain active.

The following graphic shows the trailer module (AHM) in the example F15.

Fig 1: Identifying Trailer Module (AHM)

Courtesy of BMW OF NORTH AMERICA, INC.

For adaptation to legal regulations in certain national-market versions, the following versions for the trailer module (AHM) can be encoded:

• European version
• not European version