No ground at trailer plug

[GordJ]

So I loaded the boat trailer the other day and I had no lights. When the trailer was on the ball the lights came on. Subsequently I tested the 7 pin plug and the 4 prong adapter to the trailer and had continuity to ground so the trailer ground is not the issue. When I tested the "outlet" plug on the LX there is no continuity to ground. I will be on my back in the Nov. climate so I am looking for an easy fix. I can't see the coding on the wiring yet because there is over 160 km's of dirt accumulated but I guess that I will have to clean it all off and trace it back until I find a ground?

 

[kcjaz]

So I loaded the boat trailer the other day and I had no lights. When the trailer was on the ball the lights came on. Subsequently I tested the 7 pin plug and the 4 prong adapter to the trailer and had continuity to ground so the trailer ground is not the issue. When I tested the "outlet" plug on the LX there is no continuity to ground. I will be on my back in the Nov. climate so I am looking for an easy fix. I can't see the coding on the wiring yet because there is over 160 km's of dirt accumulated but I guess that I will have to clean it all off and trace it back until I find a ground?

You want the White or White w/ black stripe wire depending on which side of the connector you are looking at:

The 7 pin trailer plug has two wiring harness connectors:

the ground is in the 5 wire plug. Unplug it at test both sides, and go from there.

 

[Sandroad]

I wonder if the easy fix will be a corroded connector. Did you thoroughly clean the connections in the LX receptacle, the 7-4 pin adapter, and the trailer 4 pin? Are all connectors in the harness shown in @kcjaz post clean and tight?

 

[GordJ]

I wonder if the easy fix will be a corroded connector. Did you thoroughly clean the connections in the LX receptacle, the 7-4 pin adapter, and the trailer 4 pin? Are all connectors in the harness shown in @kcjaz post clean and tight?

Yes, I scraped the “terminal” really well before I tested it. I will be pulling them 5 pin connector next and proceeding from there as kcjaz suggests.