What does your cluster say?

Check Fog lamps?
What codes are you getting?

If you have nothing showing on the cluster it's more than likely your switch, but if you have the fog lamps message and they don't come on in auto mode you probably have an issue with your LCM.
Try pushing the fog lamps but when in auto and it's dark out and you'll get a message on your cluster (see above) if it's the LCM.

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"When the Team Chief said.... You're trapped in a hole with nothing but a goat and a slinky, what do you do? Stubby said, I'm not sure but it won't end well for the goat...." ~(Overheard) Last day, Phase 3, Q Course