Diesel Data: Automotive Repair

Horn: Description and Operation

HORN

There are two separate conditions that can cause the horn to sound. The horn sounds if the driver presses the horn switch(es) and when the remote keyless entry is armed. The horn system uses a horn relay to provide voltage to the horns while the horn switches and the front electronic module (FEM) provide the control grounds to engage the horn relay. The horn switch is located behind the drivers side air bag. For the removal and installation of the horn switch(es), refer to Horn. The FEM is located behind the LH A-pillar lower trim panel. For removal and installation of the FEM, refer to Information Bus (Module Communications Network).

PRINCIPLES OF OPERATION

When the horn switch is pressed, a message is sent from the instrument cluster via the network communication link to the FEM. The FEM receives the message and energizes the horn relay by grounding the horn relay coil, allowing the dual note horn to sound.