Liftgate dome light and door sensor

cstraface · Aug 11, 2014

For the past few months I've been trying to trace down this problem, but haven't had much luck.

Unlike most others who've experienced similar nonoperative liftgate features (ie. wiper, window, lock, etc) I have not. The only issue I have is dome light and door open light on combination unit.

The rear dome light works when in "ON" position. But doesn't when on "DOME". I have no door open or door ajar light on dash/combo unit when liftgate is open, but I do when all other doors are open. Similarly, my front dome works fine with the other doors, just no rear dome with liftgate.

I've followed service manual for non-op dome. Checked continuity on light, and the switch in liftgate. Both are fine. I also picked up a rear door ecu off ebay, but that wasn't the problem. Also, I've removed grommets at top of gate where others have experienced shorts due to exposed wires. Mine all look perfect.

After reviewing the wiring diagram I'm thinking it has to be body ecu or combination unit. Does anyone have any advice for narrowing down this problem? Has anyone experienced something similar?

TheDurk · Aug 11, 2014

Well, before I messed with ECU's, Body or Back, I'd confirm three things.

At Back Door ECU, Terminal 7, Blue/White wire: Do you have ground with door open and no ground with door closed?

Do you have continuity from Back door ECU Terminal 18 Violet/White wire to Body ECU Terminal 7 Violet/white wire?

Do you have continuity from Door terminal 1 Light green/red of rear dome light to Terminal 12 Light green/red wire at Plug C27 on combination meter(speedo module). I'd actually check the light/green wire at Terminal 9 of plug IE2 in the left kick panel first, as that would be a lot easier than pulling combo meter. A fail from there forward to the combo meter is less likely.

Those three tests, added to what you have reported, pretty much rule out the wiring and leave you with two suspect ECU's.

I don't know, and have no way to find out, if violet/white wire signals with 12V+ or ground, but I assume it is one or the other. That's how you tell which ECU is at fault. So I'd open that plug at IE2 in the left kick panel and then see what happens on the violet/white wire from the rear at that point. SOMETHING should change as you open and close the hatch, or Back Door ECU is suspect. First test for 12V+ and then test for ground with hatch open and closed.

So Many Roads · Aug 11, 2014

Sounds like the problem you are having is that when you open the rear hatch, the dome light does not come on? I had the same problem, replacing the liftgate latch (see pic) solved the problem. I found a used one for $30, no issues since.

Liftgate Latch for 1999 Toyota 4Runner|69350-35020

cstraface · Aug 12, 2014

TheDurk said:
Well, before I messed with ECU's, Body or Back, I'd confirm three things.

At Back Door ECU, Terminal 7, Blue/White wire: Do you have ground with door open and no ground with door closed?

Do you have continuity from Back door ECU Terminal 18 Violet/White wire to Body ECU Terminal 7 Violet/white wire?

Do you have continuity from Door terminal 1 Light green/red of rear dome light to Terminal 12 Light green/red wire at Plug C27 on combination meter(speedo module). I'd actually check the light/green wire at Terminal 9 of plug IE2 in the left kick panel first, as that would be a lot easier than pulling combo meter. A fail from there forward to the combo meter is less likely.

Those three tests, added to what you have reported, pretty much rule out the wiring and leave you with two suspect ECU's.

I don't know, and have no way to find out, if violet/white wire signals with 12V+ or ground, but I assume it is one or the other. That's how you tell which ECU is at fault. So I'd open that plug at IE2 in the left kick panel and then see what happens on the violet/white wire from the rear at that point. SOMETHING should change as you open and close the hatch, or Back Door ECU is suspect. First test for 12V+ and then test for ground with hatch open and closed.

Thanks - will go through these one by one tonight...

busmup808 · Aug 13, 2014

So Many Roads said:
Sounds like the problem you are having is that when you open the rear hatch, the dome light does not come on? I had the same problem, replacing the liftgate latch (see pic) solved the problem. I found a used one for $30, no issues since.

Liftgate Latch for 1999 Toyota 4Runner|69350-35020

I too was having the same problem for the past 8 months. It was off and on though, until the beginning of July when it went completely dead. I just went to the junkyard and grabbed one. I just got done Installing it and it works! Thanks for the 411 and have a good day.

So Many Roads · Aug 13, 2014

busmup808 said:
I too was having the same problem for the past 8 months. It was off and on though, until the beginning of July when it went completely dead. I just went to the junkyard and grabbed one. I just got done Installing it and it works! Thanks for the 411 and have a good day.

Awesome. Glad it solved the problem for you. Seems to be a pretty common issue.

I have a second spare latch from a junkyard. If anyone needs one send me a PM and we can work out a fair price.

906Runner · Mar 14, 2020

So Many Roads said:
Awesome. Glad it solved the problem for you. Seems to be a pretty common issue.

I have a second spare latch from a junkyard. If anyone needs one send me a PM and we can work out a fair price.

So I did the same exact thing. Symptoms were key FOB stopped working, rear wipers and defrost didn't work. Even had the alarm going off by itself and eventually the doors unlocking constantly. Replaced the rear latch, everything back to normal. After a little while the key FOB won't work again, rear wipers and defrost also kaput. Checked the wires that are above the hatch, everything looked okay. Any ideas? Did I get a defective latch?

RodrickHeffley · Apr 1, 2023

Apologies for the bump, but I'm currently trying to figure out this issue, similar to what the OP of this thread had.

The rear dome light only works in "ON" and the door ajar light on the dash doesn't light up with the door open, but for all others it does

I have replaced the latch already but that didn't do anything, and I have checked the wire harness twice and repaired what seemed to be broken but that didn't change anything at all

I'm not sure if this is linked to the rear hatch not locking 100% of the time, but that's happening too.

The other day I was replacing weather stripping and found some broken wires under the door sill and was told they go to the back, but repairing those also changed nothing.

what should I do next?

Replacing the rear door ECU should be easy so long as I can find one at a junkyard, but what if it's not that?

Liftgate dome light and door sensor

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