I have noticed a humming sound coming from the round cap that is located on the headliner directly above the driver (I have a 2002 Yukon). The cap has small holes and appears to be a microphone for the OnStar system, but I am unsure. Before I pull off the cap and take it apart, I wanted to know what's behind the cap. The humming sound only happens when it is cold outside. Once the car warms up, the humming goes away. Any help would be appreciated.
Thanks,
Rob
Thanks,
Rob