I have changed the bulbs fuses checked the tail light circut board checked the headlight switch.
2003 gmc sierra tail lights not working.
It could happen due to a loose connection of the wire or the corrosion or damage of the wire ends.
I would second check the fuses probably the best to start especially since its just the rear cause they are probably on the same circuit.
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If the tester lights up your fuse is functioning fine.
If it does not light up then replace the fuse with another of the similar amperage and size.
If the brake light turns on you have to fix the ground connection.
Burnt out light bulbs the other reason your tail lights are not working but your headlights are maybe a blown bulb.
In many instances you can see the break in the metal strip of the fuse.
Electrical is not my strong point so any help would be.
When i checked the wires at the tail light only the wire that worked the turn signals had juice the other 3 did not.
Its got to be a fuse if not i guess it could potentially be a bad relay somewhere in the vehicle.
When i checked the wires at the tail light only the wire that worked the turn signals had juice the other 3 did not.
The brake lights turn signals reverse lights all work but the tail lights when you head lights are on do not work.
I have changed the bulbs fuses checked the tail light circut board checked the headlight switch.
Connect the light switch to a good ground with a jumper wire and press the brake pedal.