Filament Monitor, Front Lights

Filament Monitor, Front Lights

The SID unit receives information on headlamp functionality from the filament monitor.
The SID unit sends B+ to the filament monitor via pin 23. If a headlamp bulb is faulty, the filament monitor output will be grounded.
The SID unit uses the information for a CHECK message (3 second delay). See Technical description, "Service Message". Service Message

Diagnostics
If a short-circuit to ground occurs in the filament monitor circuit, the CHECK message for a faulty lamp will be shown even though the lamp is OK In the event of an open circuit, the CHECK message will not be shown even if one of the lamps is faulty.