You can download a copy of your service manual at the following link: http://www.toyota.com/t3Portal/document/om/OM48685U/pdf/01_06.pdf
A complete listing of all the downloadable manuals for your 2007 Toyota Highlander can be found here: http://www.toyota.com/owners/resources/owners-manuals?garagePrefVehicle=0&garageModelName=Highlander%20HV&garageYearValue=2007&addToVehicleList=false#
Page 155 explains this code is telling you that it will soon be time for an oil change. Looks like it's time to bring your Toyota Highlander Hybrid in to the shop for some regular maintenance.
For additional assistance, please find an AskPatty Certified Repair Shop at http://www.askpatty.com/search/?type=all&m=30&q=&keyword= and they can help you maintain your vehicle.