2013 QX56 with 140K miles recently purchased with an interior light issue. The wiring harness for the door pin-switch for the front passenger door and for the 2nd row doors have been disconnected. When I connect the wiring harness to any of these switches the interior lights are activated correctly when that door is open, but when closing the door the interior lights do not shut off completely, and remain dimly lit. The interior lights work correctly for the drivers door. I'm wondering if its the BCM, or worse?

It's possible it's a dying FET inside the BCM, but not likely if it works correctly with the driver's door. It's more likely that one of the dome light switches is leaking to ground. In almost all Nissan systems, the "door" throw of the switch connects the ground side of the dome lights to the BCM, while in the "on" position it connects them to hard ground. That means a low-grade short circuit inside any one of the switches or in the roof wiring will cause dim-and-constant bulbs. The easiest way to isolate the cause is to cut the circuit in half by disconnecting the roof harness connectors (underneath the driver's A-pillar trim). For some reason the PG section is missing from the QX56 manuals here, but I found a copy of the R1 pinout in Motor (attached below). With one of the faulty door switches hooked up and the driver's unhooked, rig a bulb-type test lamp between pins 15 (White/Red) and 31 (Brown) on the Main Harness side of the connection (away from the roof). If you get a dim light then the problem is in the BCM or Main Harness, if not then the problem is in the switches or Roof Harness. If it's in the roof, the most likely culprit is a corroded or degraded switch or fixture. Take the individual light fixtures loose one by one and see where the problem goes away.

Thanks, I will give it a try.

I do have one question, if it's in the roof, and a corroded or degraded switch or fixture wouldn't that affect the drivers door also?

Not if it was in the passenger switch or one of the rear fixtures. The lamps are actually kind of a funky setup with some series connections and at least one diode, and the BCM may also respond to the hatch switch in some way. If you don't find anything at R1 or in the roof, I'll get the PG section from ASIST at work and try to get an idea of where to look next. If you do find something in R1 then it may get really complicated trying to pick the BCM's brain, but I'll help you out.

Appreciate the explanation. I'll run the test you recommend over the weekend.

You're most welcome. Just took a harder look at the diagram and the door switches all go independently into the BCM. So the only thing on the door switch side that could be affecting it globally is the hatch switch. See if the cargo lamp also comes on when you connect one of the faulty door switches. The cargo lamp has its own control wire separate from the domes, so if it's lit it will be a clue to what the BCM is seeing.

Hmm, I think I just found something. This is from INL-7 in the ESM:

• When all doors are closed, and any all door unlock operation is performed or ignition switch is turned OFF,
BCM brightens interior room lamp to 30% brightness and maintains 30% brightness until any door opens.

This is part of the "welcome lights" function and might indicate that something in the lock system is involved. I'll keep looking.

Okay, one more test. We can find out if it's a welcome-light malfunction by disabling the function. Turn on the ignition (don't start). Within 20 seconds, press and hold the door request button in the driver's outside handle until you get a beep from the cluster (about 5 seconds). That will toggle all the welcome stuff off. Repeat to turn it back on if it isn't the problem.

Here's the latest, I connected the second row right passenger door pin-switch to check the cargo light. The cargo light did not illuminate when I opened and/or closed the passenger door, BUT I did notice that after aprox 15 seconds the dimly lit interior lights shut off? I disconnected the second row right passenger door pin-switch, connected the left passenger door pin-switch and got the same result. I followed this procedure for the front passenger door and got the same result so now I am totally confused. There has to be a reason why these three pin-switches were disconnected, and the prior owner won't respond. I guess I'll wait and see if the lights illuminate on their own or the battery is dead from a current draw?

It shouldn't go dead, there's a Power Saver circuit inside the BCM that should turn off power to all the courtesy lights if they've been lit for some extended period (15~20 minutes on most Nissan products). The Power Saver gets reset whenever you close and reopen a door. The dim lights are most likely from the welcome effect I mentioned, and if they're going out after a short time then it sounds like they're working normally. They shouldn't be staying lit, which was what I inferred from your first post. According to the manual, the behaviors are a bit different for the driver's door and depending whether there's an I-key in range of the receivers in the outside front door handles.

Maybe the previous owner was a dope dealer and had a problem with his courtesy lamps working for customers. I dunno.

Yes the lights do seem to be working normally which has me wondering why the pin-switches would have been disconnected for these three doors, and I can't get an answer from the prior owner. Guess I'll wait and see. I appreciate you taking the time to offer your insight.

You're most welcome. I wasn't kidding about the dope dealer, I've lived in some "bad hoods" and I can tell you it's very common. They do business at night and don't want anyone seeing who's coming and going from the vehicle. That might explain the lack of reply as well.

No battery issue this morning, can't believe when I first connected the wiring harness to one of the door switches and noticed the interior lights did not shut off completely, and remained dimly lit that I didn't have the patience to wait longer. Guess I was expecting the worse. My apology for racking your brain.

No apologies needed, somewhere down the road we'll have both saved someone from the same brain-racking. That's the beauty of forums, the knowledge is forever.