Nav system

[Matthewnuwk]

I just bought an 05 QX56. The radio, nav system, and back up camera do not work. The screen is black. No light at all. I replaced the "computer" behind the screen with another used one and still nothing. All fuses, or at least the ones on the passenger side dash, are good. Any ideas?

 

[marctronixx]

was this a salvaged car? was the cars electronics modified in any way that you know of? if thigns have been modified from an owner/user, that can be difficult to diagnose.

if its all factory ...

first thing is to check the obd port for any sensor faults or other codes.

the head unit could be damaged/inoperable.

can you use the AC/HVAC?

there are relays/fuses in the engine room.

there is a CCU for the backup camera in the rear. this turns on the backup lines and activates the camera. that could be faulty as well as the camera itself.

could be a wiring harness that does not have continuity.

do you have any issues with other sensors, bumper sensors ? do you have any electrical issues?

the BCM and TCM are both used to activate the rear camera. they could have some faults.

 

[jrm5f2]

Just curious did you check all the fuse in the engine bay and inside the car. The reason why I am ask is because I had an 08 Armada and while doing some work had the A/V fuse blow on me and do everything you describe. It took me a minute to find that fuse, but once replaced it was good as new.

 

[Matthewnuwk]

Not a salvage car, wiring all looks original, AC/HVAC works, I don't believe any other sensors are having trouble. I found the relays in the engine compartment, how do I check those? The fuses inside on the passenger side dash are all good.

______________________________

 

[marctronixx]

There are videos on how to check relays, but you hear then click when they activate.

If you have fogs, and they work, you can TEMPORARILY swap the fog relay to the ipdm or other relay to TEST.

 

[Matthewnuwk]

After finding the engine compartment fuse box (which I had missed the first time) I started testing fuses. I found several that were bad including the radio one. I replaced them and found that the fog light one was sparking and blowing every time I put a new fuse in. Decided to leave that one out to focus on my original problem. Went to the cab and started the vehicle but it still was not working. Went back to the fuses and started testing again but found no bad ones (other than the fog light one). Scratching my head in confusion I went back to the cab and tried again. Holy crap it worked! Not sure if I needed to start it two times to get it to reset or maybe I didn't have the fuse pushed all the way in the first time but my wife is extremely happy now.