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Stuck in H4

Discussion in '2nd Gen. Tacomas (2005-2015)' started by TheFlyingPotato, Aug 6, 2021.

  1. Aug 6, 2021 at 6:43 PM
    #1
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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    Greetings friends. I have a 2012 Tacoma that has recently given me an issue. It is stuck in H4 and won't go up or down. I've had instances in the past few months where it would try to go from 2H to 4H or vice versa uncommanded. It would happen upon starting the engine, the 4WD light would flash. Rotating the switch would not do anything. To remedy, I would place the switch in the position the truck seemed to want to be in, turn off the engine, then turn it back on. After that I would have normal command of the 4WD.

    Yesterday I ran into what I thought was the same issue. Turned the truck on and the 4WD light was flashing. I turned the switch to 4WD, turned it off, then turned it back on. Only this time, no matter what I do, the 4WD and 4LO light start to flash simultaneously. I tried turning it to H2, 4WD and 4LO flashes. I put it in N while stopped, turned the switch to L4 per the owner's manual, 4WD and 4LO flashes but never catches in 4LO. The only time I get a solid light is when I turn the truck on with the switch in H4. But as soon as I turn the switch, 4WD and 4LO flashes. As I drive, the truck is definitely in 4WD and I am assuming it is in H4, but I am inexperienced and not sure if I would recognize if the truck was actually in L4.

    The 4WD fuse is in tact. I looked under the truck at the back of the T case. A quick inspection of the 3 different plugs that go into it didn't reveal anything abnormal (nothing looked burnt). However, upon tinkering I did notice this hose had become quite worn and was no longer secured.

    I have not yet examined the 4WD actuator. I have some skid plates installed and that will have to wait until I have more time and daylight. I'm wondering what this hose is and if it could be the underlying issue. I believe there is some vacuum pressure involved with the actuation of the 4WD system but I'm not sure how the system works or this broken hose is that. Hope someone can shed some light on the situation before I go cry at a dealership.

    Thanks in advance my dudes.

    T Case Hose.jpg
     
  2. Aug 6, 2021 at 7:04 PM
    #2
    Dm93

    Dm93 Test Don't Guess

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    That is the vent hose for the transfer case shift motor, if it becomes disconnected the motor can get water in it and fail in short order.
    The system is fully electronic, there's no vacuum involved.
    You can take it off, clean it up and see if it starts working again, there's alot of useful links about the 4wd system in this thread.
     
  3. Aug 6, 2021 at 7:34 PM
    #3
    winkel

    winkel Well-Known Member

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    Yes, I'd say it's time to take that apart. When that vent fails, it's usually followed by water intrusion.
     
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  4. Aug 6, 2021 at 9:30 PM
    #4
    Geeves77

    Geeves77 Well-Known Member

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    If that ain’t it. Then exorcism is next. Lmao
     
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  5. Aug 6, 2021 at 9:34 PM
    #5
    risethewake

    risethewake Well-Known Member

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    Oh you'd know if it was in L4. It's a huge gear reduction that results in the truck being much slower and torquier, often jerky if you're aggressive on the throttle.

    But as others said, def worth taking it apart and cleaning it out, paying attention to any corrosion as well as the the solder points. If you're not familiar or mechanically inclined, just take your time. They're not very complex at all. When you're done, use some RTV to seal it back up. Replace that vent line with one of better material, maybe use some gorilla tape to protect the exposed areas as well.
     
  6. Aug 8, 2021 at 6:46 PM
    #6
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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    I think you fellas may have been onto something...

    Gonna clean it out with some distilled water and a gentle brush tomorrow and dry it up.

    Next question is what's the yellow stuff? Seems like grease. What do I need to replace that with?

    Final question (for now), what can I do to fix the end of that hose without replacing the whole length?

    Y'all are doing the Lord's work and I appreciate y'all!

    20210808_201851.jpg
    20210808_201848.jpg
     
  7. Aug 8, 2021 at 6:49 PM
    #7
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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  8. Aug 8, 2021 at 7:04 PM
    #8
    Dm93

    Dm93 Test Don't Guess

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    Not sure about the grease, I would say dielectric grease but someone else may have a better answer.

    As for the hose as long as the rest is in good shape you could use a vacuum hose and splice of the correct size and cut out the bad part.
     
  9. Aug 8, 2021 at 8:36 PM
    #9
    Leomania

    Leomania Well-Known Member

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    I just did a patch to mine (pre-water intrusion) and I recommend using a 90-degree elbow rather than a straight fitting if you decide to go that route. The hose goes behind the actuator so it gets enough of a sharp bend that this kind of failure is inevitable (after many years, of course). Patching in a short piece after cutting off the bad part and using an elbow eliminates most of the strain.
     
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  10. Aug 9, 2021 at 2:05 PM
    #10
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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    Well, no luck so far. But after cleaning out the housing, it appears that there is a lot of wear on the contacts. From what I understand, the 11 o'clock position is the H4 position, which is what my truck is stuck in . As you can see, the outer contact ring is quite worn. I don't think the circuit with the motor is being completed as it requires 2 complete contacts with the 3 forked contacts on the other half of the housing.

    Pulling the trigger on this guy: https://www.amazon.com/Compatible-Transmission-36410-34015-3641034015-NICEKE/dp/B08K8KS376

    I hate supporting Amazon, but these are desperate times.

    Tune in Thursday for an update. Keep your fingers crossed for me!

    20210809_141510.jpg
     
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  11. Aug 9, 2021 at 3:10 PM
    #11
    TnShooter

    TnShooter Well-Known Member

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    I’m pretty sure I recall someone else using the Amazon part.
    They just used the cap, reported it worked fine.

    If/when mine has this happen, I’m going Amazon first:thumbsup:
     
  12. Aug 9, 2021 at 6:39 PM
    #12
    Leomania

    Leomania Well-Known Member

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    If I recall the orientation of that actuator correctly, the section that's really bad is the one that was closest to the ground; your original pic shows what appears to be mud in that area rather than grease. So that grooving totally makes sense. Amazing so much crud could get thrown up through that tiny hole, isn't it?
     
  13. Aug 9, 2021 at 8:19 PM
    #13
    6 gearT444E

    6 gearT444E CEO & CFO @BPF

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    wow that hurt my head listening to him talk. Nice demonstration but doesn’t really know how it works or what any of the components are called lol. The grease on the inside id use some white lithium grease. And FYI you can jog the new motor into the right position using a jumper on the connector to set up the timing perfect.
     
  14. Aug 9, 2021 at 8:27 PM
    #14
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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    You're not wrong lol. But it was what I needed to give me the confidence to take this thing apart!

    Could you explain this please?
     
  15. Aug 9, 2021 at 8:41 PM
    #15
    Jensonbt

    Jensonbt Well-Known Member

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    Just enough to look kinda cool.
    I think he’s referring to hooking up wires to the connectors. So put power to the left or right and ground to the Center, or some assemblince of that. (Should check which combination is needed before just hooking wires up.) By doing this you will manually be turning on and off the actuator to put it in the correct position so installing it is much easier.
     
  16. Aug 9, 2021 at 9:31 PM
    #16
    6 gearT444E

    6 gearT444E CEO & CFO @BPF

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    Sure, in addition to "eyeballing" the limit switches, you can get it timed like it was from the factory. Keep the T4 connector unplugged. Put the transfer case shift rail into desired physical position to have the actuator timed to. Ensure final gear is removed from the actuator.

    Connect a meter from actuator side pins to desired limit switch locations, limit switch will be closed (connected to ground, zero resistance) when in requested state. Connect +12V to one side of the motor terminal (1 or 2), and ground to the other terminal through a switch so you can control the voltage easily while monitoring the status of your limit switches. If motor spins wrong way, reverse polarity at the motor connections. Jog motor until limit switches are in desired state for physical shift rail position. Reinstall the actuator on the shift rail, and install final gear on the side of the actuator and seal the cover back up with some RTV and tighten the screws. Reconnect T4 connector and you should be good to go.

    Here is the technical name for the "doohickeys" that fellow on the video was trying to describe :rofl:

    upload_2021-8-10_0-30-29.jpg

    upload_2021-8-10_0-22-25.jpg



    upload_2021-8-10_0-17-34.jpg


    upload_2021-8-10_0-20-36.jpg

    upload_2021-8-10_0-19-25.jpg

    upload_2021-8-10_0-18-56.jpg

    upload_2021-8-10_0-17-22.jpg
     
  17. Aug 9, 2021 at 9:51 PM
    #17
    TnShooter

    TnShooter Well-Known Member

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    Excellent information.
    I added a link this post in the 4WD help thread posted above by Dm93.
     
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  18. Aug 9, 2021 at 10:34 PM
    #18
    TheFlyingPotato

    TheFlyingPotato [OP] Member

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    Wow, thank you for this!

    So in my case, since the rod is in position for H4, I need to probe terminals 1/2 and 6?

    To get the 12v introduced to the system, are you suggesting literally taking some jumper cables, attach them to the truck battery, then attach probes to the other end to poke into the T4 receiver? I don't understand that part.

    Could I install the actuator with final gear removed, plug in the T4 like normal, and use the 4WD selector switch in the cab to command it where I want it to go? I feel like that would energize the system and allow me to move the limit switches where I want them.
     
  19. Aug 10, 2021 at 12:10 AM
    #19
    6 gearT444E

    6 gearT444E CEO & CFO @BPF

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    Well, I would check all 3 contacts, measuring from terminal 3-4, 5-4, and 6-4 as you cycle through the operation since there is overlap between the contact closure. You don't want to be on the edge of a contact operation otherwise the timing could be off, and it doesn't take much movement to change the positions. That is why Toyota does not want you to take it apart.

    To answer your question, no you can't allow the 4wd ECU to do it as it would complicate things. The 4wd ECU needs to also see positions of the transfer case to change via the detent switches as well as drive the motor voltages otherwise it will lock out operations. So with the actuator not driving the shift rod, those detent switches won't change position and the system will probably just sit there and blink. I don't think it would ever complete the sequence if the system wasn't fully in sync to begin with.

    The 12V can be taken from anywhere, but if it was me doing it (and would make things super easy), buy this pigtail and plug it into the actuator and connect your meter and power supplies up to the pigtail instead of trying to get on the pins inside the actuator itself. Label each wire and print out that chart, and jog the motor until you are in the middle of the H4 sequence. The 4wd ECU essentially performs this same functions based on operator request and a truth table with those limit switches to either rotate the motor CW or CCW to a desired position.

    https://www.amazon.com/NEW-Pigtail-Harness-90980-11858-9098011858/dp/B087NVTBXR

    I labeled your picture so you can see what wiper performs which function, so you can see that in H4, TL2 (terminal 6) should be connected to ground and TL1 and TL3 (terminals 5 and 3 respectively) should be open circuit.
    T-case actuator terminals.jpg
     
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  20. Aug 10, 2021 at 12:42 AM
    #20
    6 gearT444E

    6 gearT444E CEO & CFO @BPF

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    Sorry, about the power supply, you could take it directly from the battery through some test leads. What would make it even easier though would be to bench test it and use a AA battery. The bonus being that the motor will spin slower and will be easier to ensure it stops in the right spot. This is the same method Toyota suggests to do for the differential lock motor to set the timing in the event it was interrupted. So essentially all the timing checks can be done on a work bench and once you have the timing set, you go install it in the truck and put the final gear in and cover.

    upload_2021-8-10_3-40-54.jpg
     

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