[psu ody fan]

The fact that it doesn't stay up when you open it manually leads me to believe it could be a strut problem.

 

[psu ody fan]

You can go to a web site like bernardiparts.com and drill down to the tailgate for a complete diagram of all the parts that make up the power tailgate assembly. If you are handy in repairing it yourself, it should be a fairly inexpensive repair. Good luck.