Here are my est results. But read the bottom below what discovered.
Left brake tail lamp works. Test grounded taillamps but no change. No changes with wires at firewall with brake pedal. Just Brown wire power.
I plugged in the plug at the firewall and used test lamp and green, brown and yellow wires show power but connector unplugged test no power. This with nothing on. Tested with signals, yellow flashes and green goes off. Rt flasher, green goes off yellow solid. Must be a wiring issue going back from fire wall underneath ? Going to look.