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Rear fog light

Rear fog light

Description of operation



The rear fog light is turned on with the rear fog light switch. The rear fog light must be reactivated each time the ignition is switched on. The rear fog light can be turned on when the light switch is in position 1 or 2 and the ignition switch is in the ON position.

So that DICE can safely determine in which position (0-1-2) the switch (10) is, it uses information from TWICE and its own pin connection.

The parking lights are controlled by TWICE which gives information to the bus (ON/OFF). The message ON corresponds to switch position 1 and the message OFF corresponds to switch positions 1 or 2.

DICE pin 39 is connected to switch pin 5, which corresponds to position 0. DICE pin 15 is connected to switch pin 4, which corresponds to position 2.

Voltage +15 is fed to the rear fog light via DICE (628). When switch (161) is pushed in, voltage +15 is fed via fuse 19 to pin 16 on the control module. The lamp (33 HL alt. 33 HR) is then powered from DICE pin 25.

DICE sends information about the status of the rear fog light (ON/OFF). This is used by MIU (main instrument unit) to turn the indicator lamp for the rear fog light on or off.

Pin 25 on DICE is intended for a trailer connector (258).

To prevent unnecessary loading on the battery when the starter motor is activated, DICE turns the rear fog light off. When the ignition switch returns to ON from the ST position, DICE turns the rear fog light on again. The off period is limited to 20 seconds for safety reasons, so that the rear fog light will function even in the event of a fault, i.e. if there is no +54 voltage.

Diagnosis

TWICE detects the unbalance and sends error information to the bus. SID generates an acoustic signal and displays FOG LIGHT FAILURE.

DTC B1145 is activated when there is an open/short circuit on pin 25 to ground, or a short circuit to B+.

DTCs are not generated if the voltage is below 11V or during diagnostic communication.

Important

When changing a bulb, use one with the right output otherwise the components could be damaged.