Rear driver side brake light does no work

Hi,

I'm looking through the wiring schematic. It can't be a ground issue because all rear lights share a common ground. None of them would work if that was the issue. (see pic 1)

Next, have you checked to see if there is power to the light socket when the brake pedal is depressed? There is a white / tan wire that is the power supply to the left rear brake light direct from the brake light switch. Confirm if there is power to that wire. (see pic 2)

If there is no power and the right brake light and center mounted brake light work, chances are there is an issue at the wire splice (S304). See pic 3 In the picture, I have an arrow and letter indicating power flow to the left and the right. Power could be lost at that splice, or if you have a factory trailer tow package, it could be the second junction to the left light right below the splice.

The first thing I would do is simply confirm there is or isn't power to the light socket. If there is power, replace the socket. If there is no power, then there is an open (break) between the splice and light. At that point you will need to trace the indicated wire back until you find where power is lost.

Here are a few links you may find helpful:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

Let me know if this helps. Also, if you have questions, feel free to ask.

Take care,
Joe