If it's hardwired inside the HU as a sub out then I'd guess no, as you would always want a Low Pass filter on a sub out.
There's a section (from page 19) in the manual which talks about adjusting crossover settings. You appear to have 3 sections you can adjust, Low range speaker, Front high range speaker and Rear high range speaker. Although I don't know the unit I'd guess that those 3 sections refer to the 3 pre-outs the unit has.