You could use it, but the connector at the trailer end of the tongue won't match, so you would have to buy some new connectors and change it. Easier and cheaper to buy a square-4 pigtail and replace the round-9 on your trailer or splice it in and have both. Keep in mind that the 2010 RT-622 was a 5-wire (actually 6-wire) system. Use with the later hitch/harness will make the separate turn signals no longer function...just like the later trailers. You will have some extra wires. Best to connect things temporarily and test...or PM me and we can take an educated guess at the wire colors.