Clicking sound under the dash
 

Hello everyone. My first post here, and I need some advice. Recently,when I turn the ignition key to the on position, (before starting the engine) in my 2006 Silverado 2500 HD, there is a continuous soft clicking sound coming from under the dashboard near the glove compartment. It cycles about every second or two. Before I get into removing the large plastic cover under the dash where the sound seems to be emanating from, what advice can anyone suggest that would help diagnosing the issue. Thanks to everyone for your help.