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2003 CTS and 2009 CTS
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Discussion Starter · #1 ·
OK guys and gals - great job of documenting how to fix your 3rd brake light - mine is out too - but the question is how do I know it is the light versus the wiring or a fuse or.... any number of bad things? The two rear brake lights work. The 3rd brake light has three wires going to it - one is primarily orange with a black stripe(o/b), there is a solid black wire(b) (guessing ground), and a third wire primarily brown with a white stripe(br/w). The o/b wire is hot all the time - brake pedal depressed or not. The b and the br/w wire are neutral all the time - brake pedal depressed or not. This seems odd - there is no change in the state of the wiring volatges when the brake pedal is depressed. Everything I've seen on the forum so far only discusses 2 wires - a positive and a ground so I'm confused why my wiring harness has 3 wires.

Can anyone identify the wiring logic for the 3rd brake light - what wires should be hot and when - brake pedal depressed or not - lights on or not - etc.?
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