I have a similar problem.
I used a wiring harness to convert to the BOSE speakers but this didn't have a sub out lead (although it was the harness for the BOSE with sub) http://www.dvbcaraudio.co.uk/nissan-350 ... escription
I'd found an article on the net that said to power the sub via a spare power out lead whch is what I've done but vey low power and Sub options on the HU are disabled.
Any ideas?
Thanks