Your blinker lights and back up lights are not working on your 96 Chevy tohoe they worked fine until we hooked a trailer to tow and after they don't?

Chances are very good that you have a bad ground wire on your trailer or on the connector. Check the connector for rust or rot, clean the pins and use some grease to prevent future problems.

If the problem isn't at the connector, you may have a bad ground on the trailer which could be anything from an ungrounded light socket to a bad ground wire.

Hope this helps