Filament monitor, front lights: Diagnosis

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.

Fig 1: Front Lights Filament Monitor - Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.