Well... i have D3 installed in my car.. and i paid $80 more to connect the speed sensor and it still not working.. BTW i have 2007 altima 2.5 ls.. the navigation is not acurate at all...what should i do should i take it back?? i need a good advise.

Have you tried resetting everything under the learning status? Also, you can try resetting the whole system by pressing the button on the top left corner of the D3 with a pin.

i would try a 3d calibration also, in the manual.

calibrates the internal gyro.

how closely does the speed match if you hit map view then map & select vehicle dynamics?