2002 Passenger Dome light/Spontaneous Alarm Issue

[jjonez]

Skip to the third paragraph to avoid some potentially useless, or possibly insightful information.

 

Alright, so I've been slowly investigating this over the last few weeks and think I am closing in on the problem but at the same time feel completely stumped. So I bought this pathy back in June and it spends most of its time in the underground parking garage at work. However when I do bring it home it spends the night outside, and occasionally the alarm will start going off late at night, after 2am generally. This has happened maybe 6 times, so up until recently I had simply taken to disconnecting the battery at night as a temporary fix. My current work-around is this: lock all doors with keyfob, unlock ONLY driver door with keyfob, then lock driver door by hand and close door. If I understand the FSM correctly, this doesn't arm the security system which seems to be indicated by the security indicator light NOT being lit solid for 30 seconds upon closing the door. Seems to be working so far, but maybe I've just been lucky.

 

One observation I've made is that when driving with the passenger dome light set to the "door" position, it has a tendency to turn on when I accelerate and turn off as I come back to a neutral throttle or decelerate. *I believe it's important to note that the door ajar light on the dash does NOT come on when the dome light does this, but otherwise functions as it is supposed to. Usually when I lock the car with the keyfob the dome light turns off and turn signals will flash twice indicating that the doors are locked and the security system is armed, but sometimes when I use the fob the doors will lock, but the dome light will stay on and the turn signals do not flash, and the security system is not armed. I figured out that with all doors closed and locked and the dome light off and the security system successfully armed, if I pull on the top of the rear right door the dome light will come on and the alarm will go off (if the 30 second window after arming it has passed). This behavior doesn't happen on any other door. I figured it was the door jamb switch but quickly ruled it out by testing continuity of the switches/swapping them between doors. No matter what I did the behavior of the rear right door remained the same.

 

So where I'm at now: The two rear door switches are currently off the car so these doors now always register as closed. I found that with the ignition in the on position I can see on the dash whether a door is open or not (information that is provided by the switches). So, the biggest finding so far is that with the rear right passenger door open (albeit registering as closed since the sensor is gone), I find that if I apply even just a very gentle downward pressure on the door, THE DOME LIGHT TURNS ON! This doesn't happen on any other door. In addition to this, it interrupts the security arming process the same way as if a door was opened, but it does not light up the door ajar light on the dash.

 

So based off this and the accelerate/decelerate thing, obviously there's some kind of misconnection. Maybe this is far-fetched, but what I believe to be happening is the temperature change at night is affecting the connection, causing the alarm to go off. As far as I know this is not a problem at work, I have heard no complaints and I'm assuming the stable temperature in the parking garage is preventing the issue. The thing is I have NO idea what the misconnection could be. I jiggled the part of the wiring harness between the door and the body but got nothing. My only other idea is that maybe it's a bad body ground, but according to the harness layout in the FSM, the only ones pertaining to the right side and door harness are close to the very front and very back, and I've had no luck locating these two anyhow. The pictures with their supposed location isn't very clear. So that is my current progress, so close yet so far...

 

Sorry this is such a long post. But I figured the more detail I provided the more I might be able to spark some ideas. Or at the very least give anyone with a similar problem now or in the future something to chew on...

 

Thanks a lot for any help.

JJ

[Slartibartfast]

So, let me get this straight. Your door switches for the rear doors are removed, but you open the rear door and put a little force on it and the dome light comes on--but not the door ajar light.

My first thought is that the door switches (on my WD21 anyway) ground straight to the body. There's one wire coming off of them, and it goes to the dome light. So if that wire is worn through, and it's hanging near bare metal, then it could be hitting that metal when you accelerate, or perhaps when you flex the B pillar ever so slightly. I'd be inclined to tear into the B pillar and see if there's anything obviously wrong in there. How's the hinge for that door? Can you see any deflection in the pillar?

 

WD21s have a common dome light issue but it's usually the sensor for the rear hatch, which is built (poorly) into the latch itself. Hopefully they redesigned that for the R50, and it doesn't sound like it's your trouble spot anyway.

[jjonez]

Thanks for the reply. The harness layout that I've been looking at is on page 469 of this: http://www.nicoclub.com/service-manual?fsm=Pathfinder/2002_Pathfinder/el

 

The B pillar and door hinges seem completely fine as far as i can tell. And I can swing the door open and closed without the light coming on, it's just when I give that light pressure...

 

The door switches on the R50 ground straight to the body as well. But I think in this case the door switch wires have to first run up to the smart entrance control unit in the dash area, which then goes to the dome light. So based on your theory, perhaps that bundle of wires in the diagram that runs along the rocker panel could be the culprit? Now that I'm looking at it again the front passenger door switch is on the B pillar as well... Any advice on how to get at the wires? Remove the B pillar interior trim? Or the whole door? Pretty unfamiliar with this sort of thing ha.

 

Thanks.

[Slartibartfast]

Yeah, a fault in the wiring going to this smart access whatsit seems most likely to me. Taking a door off tends to be a pain, so I'd avoid that for now and go for the pillar trim. I haven't messed with an R50 much but if it's like a WD21, take the seat out first, it'll give you loads of extra room to work. If you find the plug for that rear door inside the B pillar, you might try unhooking that and seeing if pressing the door still makes the dome light kick on. If there's no change, you can rule out the door; if it changes the problem, then you may have tracked the issue down to something inside the door.

[jjonez]

Good suggestion I'll look into the door harness first. For the wiring along the rocker panel do you have an idea how to get at that? I can't find anything promising from underneath the vehicle, so my only thought is pulling up the carpet inside...

[Slartibartfast]

Again I haven't had an R50 to bits. On a WD21, you remove a line of plastic screws (very carefully, they strip if you look at them wrong) from the tread plates at the bottom of the door openings, then lift the plates off, and that releases the edge of the carpet. Then under the carpet there's a white plastic cover, and under that you've got the wiring harness.

[jjonez]

LONG overdue update in case this can help someone in the future:

 

So my half-measure fix mentioned in my first post has worked like a charm the past 8 months. That was locking the doors with the keyfob, hitting the unlock button on the fob once to unlock the driver door, then locking it manually and shutting the door. This prevents the security system from arming, so any misconnection issue due to thermal expansion/contraction becomes irrelevant.

 

But today I decided to investigate again. I removed the right side B-pillar interior trim, exposing the seat belt assembly, the rear passenger door wiring harness, and the front passenger door open/closed switch harness (important). A bunch of fiddling revealed the same issue: I could lock the car, hold the rear passenger door switch down, and the passenger dome light would turn off and the security system would activate (as it is supposed to). But if I applied just a slight downward pressure anywhere on the open door, or even on the roof rack above the B-pillar, the dome light would turn on and the alarm would go off if I had waited at least 30 seconds.

 

On a whim I decided to try the same thing but with the front passenger door switch disconnected from its harness, but still screwed into the pillar. This essentially gives the "always closed" signal to the smart entrance control unit. To my disbelief, flexing the B-pillar yielded no dome light turning on or alarm sounding. I swapped the driver/front passenger door switches around to verify that it wasn't just a bad switch, which it wasn't. I repeated the test, but this time with the front passenger switch unscrewed from the pillar but connected to its harness. I held this switch closed with my finger, disconnected the rear passenger door switch to have it register as closed, flexed the B-pillar again, and got the same positive result.

 

OK! So the problem is something to do with the front passenger door switch connections. The fact that the front door switch can register as closed even when not screwed in tells me that it is not grounded in the same way as the rear doors. Indeed the front switches have 3 wires as opposed to 1, but I'm not sure why this is. Even so I still think the issue is in the connection between the body and the screw that holds the switch in place (I couldn't incite a misconnection when just fiddling with the wires). I don't know why, but somehow flexing the B-pillar messes with that screw/body connection. I tried cleaning out the threads to no avail.

 

So my official three-quarter measure solution: I simply disconnected the front passenger door switch and left it screwed in place so there wasn't a gaping hole in the body. Now the door registers as always closed so I can lock the car normally. The only drawback is that now the alarm won't work for the one door, but having at least a partial security system and being able to lock the doors without some fancy procedure is several steps in the right direction. Since I only just did this today I can't yet say 100% that it's going to work, but I am very confident and I'm currently up north where it's quite cold at night, so the next few days should confirm the theory.

 

Again, sorry for the long post, but I figured I'd put it all out there while it's fresh in my mind, and so when some poor soul 5 years from now is having the same issue they can hopefully have all their questions answered.

 

Cheers!

Edited July 17, 2017 by jjonez