need help with left rear tail light

The left rear turn signal is amber in color and separate from the running lights that are red. The left front turn signal is working fine . This is a Freightliner chassis. Today I plan on checking the ground connection at the connector to see if it is good. If not I will run a good one from that connector to ground and see if that does the trick. If the ground is good I will check the positive wire at the connector and run a new one to that one if necessary. If both are not working I will run 2 new wired to the fixture and see if that works. I will report later today on my progress.

Thanks for the suggestions

Ken