I have 2006 Highlader Hybrid that I just purchased from a not so honest young guy who had inherited that from parents. I've been driving the car for a couple of months now and seems to have a solid power train but the hybrid system check just came on today and I heard that it could be the gas tank cap needing tightening and so I did that and after a while the message went away. I wonder if that would be all I needed to do and also what else I should do to make a complete check and service of the hybrid system. I have had a Camry Hybrid before and I can tell the battery of the highlander is in good shape and charges perfectly fine. An other issue I have with the highlander is that when the rear right tire goes through bumps on the road as I am applying the breaks, the breaks release and grab as if something disconnects the pressure behind the pads.