Volvo MC110B low flow aux hydraulics don't work?

[Groundhog]

We have a Volvo MC110B that runs fine and works fine with the exception of the low flow hydraulics. The high flow works fine. I know that the high flow has a separate pump. It has had an alarm on since day one for hydraulic temp. where is this sensor located and could this prevent the hydraulics from working? I have the service manual and the owner's manual. The service manual is pretty much useless.