Tail light not working when running but brake is 15 Colorado
 

Hello, I have a 2015 Colorado that recently started having an issue. Two months ago, the passenger tail light bulbs on the top and bottom of the assembly stopped illuminating. The driver side works fine. I removed the socket from the lens so I could change the bulb, but I noticed that it is the same bulb as the brake light and it works just fine when applying the brake. I have some plans but has anyone had this before? I plan to:
Check voltage on contacts in the bulb socket both with brake on and with the head lights on.
Check fuse but this doesn't make sense.
Check wire in socket/harness to make sure wire for running light isnt broken or loose.

Anything else to check? Or maybe buy new bulb harness?

You have to find the fuse box or the power distribution center (PDC). You will get the fuse panel under the dashboard and the PDC under the hood. The brake light switch is also to be found under the dashboard and check if its plunger touches the brake pedal arm. Any problem with the fuse box and light switch will affect the brake lights.

In case if the fuse is blown, change it with a new one. Remember that the new one has to have the same amperage of the old unit. Besides, try to find out the cause of the blown fuse. Otherwise, it will be a recurring problem.