Howdy everyone. For a while now, I've had a problem with my rear hatch. The window (up and down), wiper, and opener work just fine when the key is in the ON position without the engine running. Have not had the guts to try the window defroster due to the joys of possibly shattering the window.

Once the engine is started, none of them work as they should. The window does not roll down from the dash button and the opener actuator does not allow the hatch to be opened.

Weirder, the wiper will randomly start wiping while driving even though I did not turn the switch on to run it. Sometimes it runs for 5 cycles, other times it will run for 10 minutes straight. All with no water on the window which makes me wonder when the wiper motor will burn out.

I have replaced the module unit in the hatch with no joy. I disconnected the negative terminal from the battery once and the window crept down while the engine was running but stopped working after going back up.

I am open to any suggestions anyone might have. It is very annoying to not be able to use my window or run the wiper when it needs it. I am stationed overseas so getting to a dealer will not be in the cards.

Would there be a reason that the rear wiper, window and opener work when the engine isn't running but not when the engine is?

Thanks everyone!

Sounds like a wiring issue. Did you check the rubber boot that the rear hatch wiring harness channels through? (Top left)

This seems to be a common issue.

Hopefully it doesn't look like this one... (picture from another thread)

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Thanks. I gave it a look and both ends of the grommet look good. Would it be wiring if all the components work just fine when the engine isn't running?

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It does sound like something wiring related has flaked out. Have you looked closely at your fuse panel for anything out of the ordinary like a blown fuse, burn marks or scoring, melted wiring or plastic? Same for behind the dash window switch. I'd even go so far as to remove kick plates and door sill trim to visually inspect any wiring going to the back. If everything works properly with just ACC ON then nothing after you roll on the ignition then it's reasonable to assume that one or more electrical components like a relay or sys diagnostic coming online is failing somewhere and faulting the system. Is the computer throwing any codes?

Check the ECU-B 10A Fuse

Have you taken on water anywhere? i.e. the hatch which can get clogged drain holes much like the sunroof. A-pillar (drivers side) water leaks from a clogged sunroof drain is common. That water may not drip where you see it right away but it can definitely find its way behind the dash and down the firewall to where all your moisture sensitive fuses, wiring, and electrical connectors are. I had this problem with my 4th gen and it caused the horn to start blasting randomly which was quite annoying.

I know that the hatch has a lot of things going on and its ECU is tied to the security system. The 4runners computer may have to relearn the setup when the negative cable is pulled or a major electrical component is changed out. Though, I've never run into this myself. The owner's manual has instructions on how to relearn the system.

Electrical issues are fun, ain't they? Good luck!

Have your battery "Load Tested", I know this sounds weird, BUT the rear wiper randomly coming on is a sign/symptom of the battery going bad, so it worth having it load tested just to rule it out.

That being said it's just usually one swipe of the wiper when you turn on the ignition and start the engine, but a low battery can do some strange things with computers in modern vehicles, so as stated worth testing the battery.

Here's some links on this symptom.

Strange rear wiper issue

My rear wiper has a mind of its own! - Toyota 4Runner Forum - Largest 4Runner Forum

Rear wiper cycles one time when vehicle is started???? - Toyota 4Runner Forum - Largest 4Runner Forum

Any modifications from stock? New head unit, rear view camera?

I agree youre looking for something electrical - battery, wire short, or a bad key cylinder, hatch lock actuator or harnesses

Good luck

@Wiseguy813 - As @AuSeeker suggested, I would start with the battery and by extension, the alternator. The load on each is something that changes with the engine running or not.

Also, giving your truck’s year & mileage is helpful when asking questions like this.

Sorry that is true.

2008 V6 SR5 146k

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Yes, it had a SONY head unit when I bought it and I added a backup camera but it didn't tie into the unit at all. It was a stand alone dashcam/mirror. All hatch components still worked after I installed it

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So I would check any grommets you drilled or ran the wire through as shown above