JMat

I apologize if this has been covered before but I've done searches and can't seem to find anything close.

1998 4Runner can't get rear liftgate window to roll down, defroster and rear window wiper won't work. What I have figured out is that the sensor that lets you know the rear door is open or not isn't working either as the rear dome light won't come on, when set to the door position, and the open door light on the dash won't come on when the door is open.

The weird part of all this is if I have the liftgate up and move the rear dome light from the off position to the door position the light for the rear window defroster on the dashboard comes on(but the dome light does not come on) and can only be shut off by turning the ignition to the ON position, same thing happens when I put the key in the liftgate lock and turn it. For some reason turning the ignition to ON resets the defroster light in both cases.

I really need help with this one... My guess would be a relay of some sort but don't know where it's located or how to diagnose. Thanks, John

habanero

The most basic and first very easy to do step because it's common in the 3rd gens-
Check under the boot that runs from the body to the hatch, at the top. Broken wires?


I also had a problem with my door open switch (but not with the weird stuff yours is doing) so I dug into it and posted what I saw here.
https://www.yotatech.com/forums/f200...1/index22.html
post 427 and on
I am absolutely no mechanic and don't even play one on tv. The thing I took apart is expensive to replace. Sometimes people can get them to work by spraying a bit of lube in there, I don't know of anyone else crazy enough to have dismantled it. Start with the wires. My problems were actually a combination of wires and switch.

JMat

Thanks for the response habanero!!! Thanks for the link to the report you'd posted on getting to the switch on the liftgate as I had no idea of how to do it.
My first thought was the switch too but that whole defroster light coming on has me really thrown for a loop.

Anybody else have any ideas?

habanero

So those wires under the boot between hatch and body were all good, no cracks, no bare wire, say, touching things it shouldn't?

JMat

From what I can see there aren't any issues but access is difficult at best... The way the wiring harness is wrapped makes it difficult to see much more than an inch or so of wiring. Is there any trick to gain better access for a better view?

KZN185W

iTrader: (1)

the rear hatch has computer box of some sort. you might like to open it and see if there's some moisture inside the box or some rust that may cause some grounding of some sort.

TheDurk

Well, I'd guess your problem is in the front, not the back. The Rear defog is controlled by the BODY-ECU by the drivers knee. When the back gate opens, the on wire from the rear def switch gets the ON signal from the rear door switch, (probably from the wire that carries the signal to actuate the door open light.) This is just a momentary on that actuates a timer--the rear def turn off from a timer, another push on the switch, or turning the key off. I'm guessing the key off signal gets repeated when the key turns on, causing the behavior you see.

What happens when you open the rear gate twice? Does the rear def light go back off the second time? That would prove I'm right.

I don't see how this behavior could happen from a short in the back because the rear def control circuit is all in the front. The only thing that goes to the back is the black wire that carries the 12V+ to the def heat wires.

Rear Def Schematic

Interior Light Schematic

Specifically, this would be a short between the lt.green/black wire at pin 18 of the Body-ECU and the green/white wire at pin 22--or a defective Body-ECU. Anyway, that's my guess.

JMat

Thanks TheDurk... Went out and tested your idea and the rear defroster light stays lit and won't go off until the ignition is turned on. Thanks for the schematics too!!! Those will certainly help.

I hate to just start throwing money at ECU's without any idea whether they're the problem or not and I have no idea how to test them. Any body think it could be an issue with a ground wire issue? I've seen some pretty strange things happen in cars before because of a faulty ground wire, it's always had to do with lights but maybe is the same kind of thing here(I'm just reaching for straws right now because I'm horrible at chassis electrical). Looking at the schematic I now know which color the ground wire is so I think I'll start chasing that. If that doesn't work I guess it's off to a mechanic to test the ECU's.

Blind an

Check your rear gate safety switch chances are they stuck in close position. Or is going to ground. Nothing should work or come on When the gate is open. I do believe you already know that the interior light should come when the gate is open. Or even when you open all doors. So remove panels and look for that safety switch. It should be located anywhere around the door jam or the doorlatch.
It's best to have a multimeter to check for continuity.

JMat

Used the schematics that TheDurk posted yesterday to chase the wires... Cut away the nylon wire wrap to gain access to the wires in the wire harness and found a broken wire and another where the insulation is cracking. Neither one of these wires was shorting because I've completely isolated them and still have the same symptoms. Based on the schematics posted yesterday it appears this is a ground wire(white/black) that's broken.

How do I fix this? It's about 2" into the body of the body(on the truck side not the liftgate) so I can't get in there with my fingers and with tools it's tough because of the small access hole. How would you fix this? Replace the whole wire harness or try to strip the insulation and use wire joiners? Or is there another option?

Thanks

JohnVT

It's been a while since I did this on my 2000 4Runner, but it seems I removed interior trim on the tailgate, and on the ceiling just inside the truck, and had enough access to run a splice through the trouble spot where the bundle gets pinched (well, where it bends and has the least space). I believe I had two wires to replace. Just be sure to make good connections and to use sufficient guage wires... good luck.

snopro

Hi! I realize this is an old thread, but I have a similar situation, but not exactly as described above.
My deal- 96, SR5, 4x4, man tran, 3.4l. It seems I have an intermittent short in the rear window, sometimes it works (rarely), most often not. When it works, the rear dome light works, otherwise not. No problem with either the rear wiper or defroster. Where should I be looking? When it works, it works perfectly. It’s either yes or no... Appreciate any comments!

fierohink

first, start your own thread. You can provide instance specific information and as you said you have a similar issue but not exactly.

second, check all the grounds in the rear hatch. There is a bundle of harness that comes from the body to the tailgate near one of the hinges. Take the trim panel off the tailgate and look where all the wires go to the different components. See if they are corroded or what the condition is. Then get back to us. It could be the control module that’s back there. It could be the door switch. Or a few other things.