1993 c1500 suburban taillight issue

Unfortunately, brother. We're gonna have to go the hard way, if you haven't found it already.

On the side that doesn't work, hook up a test light and see if it lights up when you hit brakes or use blinker. If so, bulb is bad. If not, continue on to next step(s).

You'll have to take some trim loose for this part. You need to open up the back (panels on both sides, as well as pillars holding headliner at the very back) and drop the back of the headliner enough to be able to see/check wires. Determine what color wires go to the nonfunctional lights. Check for power on the wires going into the plug harness. If no power when calling for lights to turn on, keep going.

Check the ground wires for the bad lights. Make sure they're good. Not broken, they're connected, etc.

Start tracing them back. They'll go up and over to the driver's side. The brake light most likely ties into the one for the DS brake light. Turn signal wire should stay separate. Just trace them back until you find a break or where they may have been pinched hard by something. Could look intact but pinched while being broken inside. Test for power once you get to the DS of the vehicle. Keep tracing and checking. You will find the problem eventually.

Believe me I HATE having to do this. But its the only way. You may end up following all the way to the dash before finding the problem. But you will find it.