LR4 Tailgate not opening

greiswig

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Does the key fob still open it?

I was thinking the voltmeter might help because it was actually switching voltage to the actuator. But thinking a little harder, maybe the wiring just goes to some BCM somewhere and tells that to close a relay that's set on a timer anyway. That does seem like the LR way. Why do something simple when there's a complex way to do it?

But maybe that means there is something the GAP tool can help isolate?
 

ryanjl

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Yeah, the rear hatch button on the keyfob opens it 100% of the time. It's weird to do it that way, because you've got to be pulling on the liftgate the same time as you press the keyfob. But it works.
 

ftillier

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Are the leads the same color wire between the two switches? I wonder if they might have changed the wiring such that you'd need to check which is which, and not rely on the colors.
 

ryanjl

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Same color. Both the existing wires are black, and the wires on the new switch are both black.

Just to be safe, though, I tried running the new switch either way, with the same result.

Also checked codes, and there are none. There is no fuse I can find that is directed at the liftgate, either. Also replaced the battery in my keyfob thinking maybe it didn't have the juice to alert the proximity (even though all my other doors work fine). No change.
 

ftillier

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Can you check for continuity between the leads with the button unpressed and pressed? Presumably it just shorts the two leads, with little to no internal resistance. If that's the case, you could try shorting the leads from the wiring harness and see if you get anything. Does the button activate the release if the hatch is already open?
 

ryanjl

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I assume you mean checking the continuity in the switch? I assume that's what it does since it doesn't seem there's a rhyme or reason to polarity of the wires (since they were both the same color). That, and my research has turned up some others with an issue whereby their liftgate just randomly opens, and that turned out to be a short in the wiring somewhere.

That in mind, I already tried shorting the wires still in the LR4 together with no luck.

But yeah, the switch normally works even when the tailgate and liftgate are both open.
 

jlglr4

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Electrical diagrams attached. I think the switch just connects ground to the BCM, and the BCM then sends a signal to the motor. Looks like there is a connection in the passenger side A panel area, and the ground goes up inside the tailgate trim someplace.

If shorting the switch wires doesn’t activate, I would suspect a broken connection on the ground side. Maybe try shorting the switch to a known good ground.

Also, check for codes - we saw one instance on the forum where a short in the actuator triggered a code that kept the circuit from firing. Clearing the code fixed it.

Hope that helps. Out of town, so not checking the forum often right now.
 

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ryanjl

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Found the problem today.

Tore into the liftgate. Removed the lower trim on the inside of the lifgate, which reveals the connector for the wiring that supplies the things inside the rear handle (liftgate release, license plate lights, and backup camera).

The new cheapo Amazon liftgate switch I got was the wrong one as it contains no wiring for the backup camera. But I was able to use it for diagnosis. I unplugged the existing wiring and plugged in the cheapo Amazon unit and the liftgate release on the cheapo Amazon unit worked fine.

So then I used my multimeter between the existing wiring connector and the wiring for the liftgate release, and there was no continuity on one of the wires.

This is what that correct harness looks like:


That's about $280. Once I saw that price, I knew I was just replacing those wires on my existing harness.

Easiest way to get to the existing harness is to just remove the entire liftgate handle. Did that and replaced the two liftgate wires. Could easily tell which one was the bad one as I could see a break in the wire once I pulled it out of the loom. Not exactly sure why it went bad as I've never messed with this wiring before, have never been in an accident, never had a problem with the rear liftgate before, etc. But the wiring for the liftgate is very thin and very brittle, so who knows.

Tested it a bit without putting anything back together and it works fine. Buttoned it all back up and it still works fine.
 

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