Horn Switch (41)

Horn Switch (41)

Main task
Used to control the horn. CIM sends the switch status on the bus.

Type
Single pin switch integrated in the driver's airbag. The switch is connected to the Sentronic circuit on automatic cars.

Connection
The steering wheel buttons are resistive multiplexed (5 V) and divided into 2 circuits; switches for Sentronic, horn and SET in one circuit and other buttons in the second. The 2 circuits have a common ground from the CIM. Each circuit has an extra resistor for diagnosing an open circuit. The lead for the Sentronic/horn/SET is fed with 5 V via a 560 ohms resistor integrated in the CIM. When the horn switch closes, the lead is grounded and the voltage drops to 0 V. All the leads go via a coil spring to the CIM. The CIM sends the status of the horn and the other buttons on the bus.