For those who have had problems with your tail lights or the harness itself I'm liiking for some info. I've got a 94 Firebird with some possible common issues. The harness that runs from the hatch area plug on the left rear then runs out too the tail lights needs/needed repair. Ive spliced some new connectors on the drivers side since all but the small one were missing. Spiced in the two 2057 bulb sockets and the 1156 bulb for the reverse light. Got power 12volt running to them and are bright. Signals work and brake lights work. The undisturbed passe ger side of harness is giving me some trouble. The bulbs are dinmmer and the vtage is 10-11volts on all positive poles. I know the ground wire was broken but repaired that and no change. I dug into the harness and found a spice that was wrapped with black duct tape. After removing was corroded but can't decide if its a factory splice since all the grounds come together and splice to one wire then splice again to another bundle of grounds and continue to the passenger side of the harness. Ill attatch a poor quality picture but will try to get another this evening.

This splice only pertains to the ground wires as the other powered wires of color are point to point through the harness. Somewhere ime loosing some voltage thats preventing the passenger side from recieving full 12volt power. I am thinking it could be the ground that is spliced causing it to be weaker not being one continuous wire for each ground but it connects the same on the drivers side coming from the left side splice pictured. The bulbs are all new and incandescent(not LED). When applying the brake lights the lights on the passenger side are brighter and the drivers side are dimmer as shown in the picture.

I will try to get voltages with the brake lights on to see if I've got voltage drop on the drivers side in the brake on scenario. Any advice on the wire splice pictured and where to look for this voltage problem would be appreciated.

 

If your sockets corroded for a while your small ground wire is probably tarnished inside. My tail lamp ground and the other below it (tcc switch i believe)

I cleaned mine and have to xut back to clean copper solder a wire in with a new end. That thin qire gets hot with rusty sockets and over time bakes the copper black inside the 18 gauge 4 strand ground for all those darn lights.

I also believe our tails and brake lights circuits go through the turn signal switch in the column as well.

I jave 4 new brake/tail sockets coming and those plus new clean ground wire going back into the harness are the last fix.

Are your blinkers slow?

 

Also I was as bright as your lamps until I stuff a dremel wire brush cup into each socket on 10 for a minute or two.

The drivers bulbs had melted the lead contact pads from resistance and corrosion. That lead to cooked ground wire im rectifying as above.

Clean the ground under your drivers seat to bare metal and the bolt on point for the tails to shining bare metal also and 600 grit the ring terminal quick to see if you gain light output and lose heat generated in the lamps.

Sorry to double post but 1993 trans am and dealing with this exact thing myself too at this time.

 

Thanks for the reply meant to provide an update. After looking over more of the harness the crimp is indeed a factory splice for the ground wires to each pigtail/plug. They come out of harness in trunk then splice combining the grounds that then run to each plug. Then the one small 8" wire splices again to the grounds for the passenger side. A previous owner removed the factory shrink tube that covered it and sealed with duct tape that allowed it to corrode. Continuity is good and resistance was good. Now for the dim and bright lights. When i wired in the pig tails i put the yellow wire where the brown wire was supposed to go. Doing this caused the wrong filament to light that has two filaments. After finding my mistake i switched them and now working as it should. There was a lot of checking with a volt meter but was the mixed wires.