My dash is saying a brake light is out

Hi and thanks for using 2CarPros.

The first thing we need to determine is if there is power to the bulb or if there is a ground issue. With that being said, I need you test wiring for me.

You can do it with a simple test light. Here are two links. One explains how to use a test light and the other, how to check wiring.

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

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

I attached a portion of the exterior lighting wiring schematic. The right brake light power supply is via a green wire with a red tracer. See attached. You need to remove the light assembly and locate that wire. When you do, using the test light, check if there is power while someone presses the brake pedal.

If there is power, that tells me either the light socket is bad or there is a grounding issue because the test light itself provides a new ground. If that is the case, we will need to start checking the grounds for this light. However, one thing at a time. Confirm if there is power.

If there is no power, we need to trace that wire back to where it splices together with the other brake light power. The splice may be bad or there could be a damaged wire.

Let me know what you find or if you have other questions.

Take care,
Joe