[jaybeecon55]

1. Double check to make sure that you have a good ground. Not just grounded to the trailer, but a hard wire ground throughthe connector.
2. Find another trailer to hook your truck up to, or find another tow vehicle that can be hooked up to your trailer. This is the quickest and most foolproof way to figure out if you have a problem with your truck or trailer.
3. If it turns out to be the trailer and your trailer is the type that runs negative through the frame, check for all the mounting bolts through each light. It's very easy after a few months for these contact points to get enough of a coating of rust to make a poor connection.
4. Don't put all your diagnostics into meter readings. A poor electrical connection can read good on a meter yet still not be good enough to power up a light.