2016 Rear tailgate functions broken

Trying to repair my tailgate window and could use some help. I've searched several posts and browsed but still can't find the answer. But I did learn a fair bit, for sure.

Problem started out when we put the rear window down and it didn't want to go back up. With some assistance we managed to get it to go back up, but it had some seriously sticky spots.

Figuring the motor was shot, I bought a new one to replace it.

While replacing it, I noticed that the tailgate had a lot of fine dust in it. So I cleaned the regulator tracks and surrounds as best I could and shot everything with silicone.

When it was disassembled, I tried to raise the glass and helped it along by pushing up from the inside. There were some serious rough spots to get over. So now I think about a new regulator. At this point, the button on the console stopped working and I needed to use the key in the rear. Even then, functionality was intermittent.

So Friday I put in the new regulator. No problem installing and when I reassembled and used the key to put the window up it went smooth as silk, and seated nicely in the window gaskets. Then....the key won't make it go up, or down. Completely dead.

Also noticed last week that the wiper/squirter doesn't work either. I know if the window isn't in position it won't work, but now that it is up tightly, I think that logic should be met.

Now, nothing in the rear works. I'm thinking I blew the ECU because I never disconnected the battery while unplugging and reseating the connectors.

I've checked fuses and visually inspected wiring.

Here's my big question: Is there a way to debug the ECU, other than basic testing of input power with a meter? Yes, it is an obvious place to start, but if there is a way to read the logic on the pinouts with a scan tool this would be an easy fix. Is that possible?

I can't imagine that Toyota techs use the methodology of "when in doubt, swap it out".

The exact ECU I'm referring to would be the "Tailgate Liftgate Multiplex Control Module 89222-35030"

Sorry for the long post, but everyone is going to ask me these questions anyway

 

Just spit balling and I don't recall reading about it being an issue on the 4Runner but have you checked where the wiring runs from the body to the tailgate? On some vehicles I've seen in the past those can be come frayed and short out from the door being opened and closed over the years.

 

My son visually checked those yesterday but I have yet to do anything with a meter like "beeping" them out. I'd like to have a wiring diagram first if possible. But I will check the input voltages today and walk through some of the steps in the manual.

Thanks

 

Did you try disconnecting the battery for a short time and reconnecting it to reset all the ECUs?

 

haven’t done this yet. Worth a try.

how long? 5-10 minutes enough?

and just the ground?

 

5 minutes would more than abundant. Just the ground terminal is fine; fewer sparks that way.

Never opened the tailgate interior panel myself, but there should be a position switch that senses if the glass is up. The switch or wiring could be bad.

 

Disconnected for 10 minutes. Still nothing working.

 

Interestingly, there is no discrete position switch identified in the wiring diagram, so it must be integral to the window regulator. There is a LIN bus digital data line going from the window regulator to the door ECU shown in both the power window- and rear wiper wiring diagrams, so that must be providing window position. Congrats, you bought into Lexus levels of maintenance costs...

Check the 30A DOOR BACK fuse is intact in the interior fuse box. Use a test light to make sure both ends of the fuse has power.

Check wiring continuity going through the tailgate flex conduit.

Check visually all the connectors and potential wiring chafe points for "green crusties" copper corrosion in the tailgate. The tailgate leaks water due to the sliding window, and is usually the first body panel to rust out.

 

There were no wires/connections attached to the regulator, so not sure how that would work.

I'll recheck the fuse in case I busted that.

If the ECU was faulty, would it throw a code, and if so would that code be in the readout of a generic handheld OBDII reader like I have?

According to the manual:

"If communication cannot be performed through LIN communication because of a break in the communication lines or some other reason, the master control ECU of the relevant system stores DTCs."

 

I'm going to measure some of the pin-outs as described in the manual.

Further to my question above, are these body DTC codes only readable by Techstream level devices?

 

The wiring diagram shows the motor and regulator as one block. Looking further in the service manual, the motor can be removed and installed separately but requires a relearn process after install:

 

Were there any instructions on how that is done?

 

Service manual exerpt attached. My best guess at this issue.

Also the service manual says to grease the two window regulator tracks before install. Did your regulator come well-greased out of the box?

 

Don't troubleshoot it. Just keep on throwing expensive parts at it.

Maybe you'll get lucky...

 

Replacing the window regulator and motor were a good call if the glass movement was visibly sticky. The cable & track style window regulator used in the tailgate is known to be problematic. My father's made-in-Japan Subaru had this kind in the doors, and three out of the four had to be replaced. Thankfully the 4Runner uses a scissor-style regulator in the four doors, so we have only one trouble spot instead of five.

 

Yes, the new tracks had a nice coating of grease. Its a great medium for collecting the next 10 years of dust.

Fuse is OK. looks new and 0 ohms

Test 1 and 2 from the manual pass. That would be the tests on V2 and W9 connections for GND and +12. However, finding an adequate body ground is not easy with all of the isolated fasteners so I cheated with a wire directly to the battery ground. Test results are supposed to be <1 ohm and I got about 4.0 when testing the grounds. But there are a lot of test leads and connectors in between.

 

Thanks for the reset procedure. I just gave it a shot but I still get no movement.

 

Would a DTC code such as "B1287 Back Door ECU Communication Stop" or any other codes arise if the ECU was dead?

Would I be able to read such codes with a generic scanner? I have a very basic Autel MS300.

 

^No. Basic scanners can read generic OBD2 powertrain codes. The other modules require a more advanced scanner to read. Those scanners also have bidirectional control, so they can run system tests to isolate the problem more quickly.