I traded in my 2007 for a 2011 PRO-4X a few weeks ago and the lights have been driving me nuts. I set out to make the fogs work any time the tail lights were on and the off road lights work any time the ignition was on. However, I also wanted to keep the look of the vehicle stock an not bypass any of the major safety features or over load any circuits. Having a background in electrical engineering helped, but I can't thank you guys enough for the help you've given here. As such, I thought I would share my electrical modifications since I don't think anyone has posted modifications that keep all of the safety features in place.
First, with the exception of the fog lights and the trailer lights, the lighting and electrical wiring diagrams in the 2009 factory service repair manual are accurate for the 2011. (http://pdf.textfiles.com/manuals/AUT...a/2009_Xterra/
EXL.pdf is where the lighting diagrams are).
Fog lights mod:
To really make this work the way I wanted, I combined the following two mods:
I don't like how the first is an "always on" sort of thing nor do I like that it loads a previously 10A circuit with up to 25A. So, I used the fuse tap to give me a positive voltage when the tails were on and I used the stalk mod to let me know when the switch was on (note, I wired a positive voltage to the stalk instead of a ground). The resulting circuit was two relays in series wired directly to the battery and the fogs (I actually wired it to the fog lights circuit in the fuse box).
Off Road Lights mod:
This took a lot more work. I originally started with https://www.thenewx.org/forum/showthread.php?t=30851
however, I really don't like that this bypasses the cover sensor and doesn't use the stock switch (again, I really wanted to keep the stock equipment). With a little bit of work, I was able to solve both problems.
Using a flip flop circuit, you can utilize the (negative/ground) pulse sent by the stock momentary switch.
After a fair amount of testing, I found that the cover sensors will ground their circuit to the BCM when the covers are on. Using this and another relay, I was able to create a circuit that obeyed all of the safety features and didn't require severing the wiring harness (I was able to tap in using wire taps).
Note: It is intentional that the Ignition +12V is wired to 87a (normally closed). This is so the cover sensors can break the circuit when they're on.
A digital/IC flip flop (a pulse SR Latch or equivalent) can be used since the currents are minimal, however, I like the idea of a mechanical switch instead just to make sure melt downs wouldn't cause a back current. I found this http://www.the12volt.com/relays/relaydiagram23.html
and it worked great.
I would post pictures, however, the links I gave really already give you everything you need and the pictures of the BCM and wiring harnesses weren't useful at all. If you go for the off road lights mod, make sure you study the diagrams in the manual, particularly page EXL-73 and the pinout description starting on EXL-109. Thanks again for making such a helpful community. I hope this is able to help someone else with the same concerns I had.