2000 sonoma lighting issues

[Austin4820]

Recently I got my first vehicle.
A 2000 GMC Sonoma SLS Ext. cab.
It has many little issues but only 1 really bothers me and actually effects my ability to legally drive the truck.

The taillights are a total mess.
When I turn the lights on, everything looks fine.
However, when I press the brakes, the reverse lights come on and the brake lights do nothing.
Then, when I put it in reverse, the entire right light goes out and the left one does nothing.
I have a little experience with electronics. But when it comes to automotive electronics, I'm absolutely lost.
Any ideas?

~Austin

 

[lmleck]

Check the ground wire at the left rear corner on the frame under the bed.
Look for a cut and splice in the wiring, as if from a wreck repair.
The bed cable plugs into a connector on the frame in the rear.

 

[drwet]

Agreed. Your problem is a bad ground. The current is finding another path and causing weird symptoms. I had exactly the same problem with my '03 when I got it. The solution was to find the ground connections at the frame and clean them up. They were corroded and not making contact. Once they were cleaned up. everything worked fine.

 

[Austin4820]

Returned from a beautiful respite; going to check the ground tomorrow morning.
If you guys are right, i will never look at forums the same.