Backup Light Circuit
Check for excessive resistance in a problem connector by performing a voltage drop test. This backup light circuit has two connectors. One of them is dropping over 3 volts. Three volts is too much voltage drop. There should be little or no voltage drop across this connection. A loose plug will result in an intermittent connection, and female connectors can become spaded.
A loose backup light plug causes the light to flicker on and off or not work at all. If there's an intermittent fault in an electrical circuit, inspect all of the connectors included. Loose connections cause damaging heat that can melt wiring and connectors.