GM Service Manual Online
For 1990-2009 cars only

Domestic

With the Headlamp Swith in the HEAD or PARK position, voltage is applied to one side of the Fog Lamp Switch. When the Fog Lamp Switch is closed, voltage is applied to one side of the Fog Lamp Relay Coil, energizing the relay (the other side of the coil is grounded through the HI Beam Filament of the Headlamps).

When energized, the normally open contacts of the Fog Lamp Relay close, allowing voltage to be applied to the Fog Lamps.

When the HI Beams are activated, ground is removed to one side of the Fog Lamp Relay Coil, de-energizing the relay and turning off the Fog Lamps.

Europe

With the headlamp switch in the HEAD position voltage is applied to the fog lamp relay circuit 10. When the foglamp switch is turn on a ground is inputted to the BCM through circuit 187. When the BCM recieves this ground from circuit 187, it then sends an output ground signal to the fog lamp relay through circuit 1977. At this point the relay in the fog lamp relay is energized closing the internal switch. Voltage is supplied through circuit 9, the fog lamp relay and then circuit 122 to both fog lamps. The fog lamps turn on when a ground voltage is applied through circuit 122 and ground is provided through circuit 1250.