The Fog Lamp Switch is part of the Multi Function / Headlight Switch on the Steering Column (turn signal switch)
The fog lamps operate only when the headlamp switch is in the ON position and the operator has selected LOW-beam operation. When the headlamps are in HIGH-beam mode, the fog lamps will not operate.
You may want to check / replace the Fog Relay located in the PDC:
Check for a blown 40 Amp fuse in cavity 14, and 15 of the PDC. If this fuse is blown the headlamps will not operate.
Check for a blown 20 Amp fuse in cavity 10 of the junction block. If this fuse is blown the right low-beam headlamp will not operate.
Check for a good ground at the right frame rail for the right fog lamp.
Check for a good ground at the left strut tower for the left fog lamp