Ok I understand the connector is all busted. That's OK. So strip the ends and test just the hot side first. If that shows good, twist each pair back together tightly and proceed with socket test. After the problem is found, and if wires are good, you will do a proper splice as referred to earlier. That connector is not needed and adds resistance and corrosion points. Any connectors along the way back there should eventually be eliminated. They were only to facilitate the assembly line.
I understand you did a visual color or wire observation. Some logic to that. No issue.
My take on buying a $10 tool: Many times we need to do a good easy troubleshoot to find out where voltage is or is not. For lighting issues, starting issues, switches, electric motors, gauges, lighter, heater, wiper.......... We know it's 12V. We don't care about amps or ohms, we are not looking for continuity or any AC. Just looking to see if voltage is reaching a certain point.
Multimeters are good tools, amps, ohmage, continuity, voltage drops, spikes. Gives specific values for testing certain components, battery and charging.
If you want to do the test for a blinker, which is an on/off flow, with a multimeter, that won't simulate a bulb flash, go ahead. I will work with that as best I can.
The ice pic is WAY better, faster, easier, more effective and accurate for lighting issues and many other issues. We need to chase the voltage up stream from the failure to find where it starts and stops flowing. As well as testing and confirming the ground. Get the ice pick tester and use it as described. Nothing to read, no mode to select, no range to select, no mistakes, no delicate cumbersome meter to keep from dropping. You will like it. When using it to test for voltage, you get continuity for free. With this issue, you are not looking for "readings" or to "buzz out" a circuit.
Let me know what you find out. Your issue, while fairly common, is difficult to find sometimes. Grounds are very weird. It's not a wire to check, it's the whole truck!!! We don't really know if it's ground yet. Waiting on you
