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[SOLVED] [Automatic Transmission Failsafe Mode Troubleshooting] Transmission Control Computer

Discussion in 'Daihatsu Hi jet' started by MrJPolito, Oct 14, 2021.

  1. Ronso

    Ronso New Member

  2. MrJPolito

    MrJPolito Active Member

    I have just received a Japanese service manual for the S110P Hijet (and other models from 1994-95, probably other years). This thing is crammed full of info and I'm surprised that it's so hard to get ahold of. I had to buy one from Aleado (basically Yahoo auctions in Japan), who then received the item from a local seller and shipped it to me via Japan Post. If you aren't aware of Aleado, they're fantastic for auto parts and other Japanese things that you need and can only buy from Japan.

    Here's the service manual, with list of models on the front:


    Let me know if anyone needs anything from it and I will try to look it up. Might also try to scan this thing somehow. I think the library at my university offers a scan service.

    The first thing I did was look up the diagnostic system in the vehicle. I use the Google Translate app on my phone to translate what my camera is seeing.

    PXL_20211115_205030246.jpg original_3d4fbc3d-7704-4ba4-a9e1-02532809ae90_PXL_20211115_204541698.jpg Screenshot_20211115-124445_2.png Screenshot_20211115-124407_2.png

    Aside from just retrieving engine codes, you can short quite a few other terminals to get codes from other computer modules, including transmission control, power steering, and ABS.

    Next I looked up how to retrieve and clear the Automatic Transmission codes:

    original_b086cb0a-cf11-45ea-8c51-4e77263d5485_PXL_20211115_214933450.jpg Screenshot_20211115-133634_2.png Screenshot_20211115-133652_2.png

    Insert a jumper wire between terminal E1 and T1 on the diagnostic port and turn the car on in the accessory only ignition position. The PWR light will flash on the dash, and the number of flashes corresponds to an error code being saved by the transmission computer. To clear the codes, remove the PMNT fuse (the reverse lights) for ten or more seconds (this also clears all ABS and power steering codes).

    Here is a chart showing what each displayed code means:


    Continuous flashing, no pause - No error codes
    21 - No. 1 Solenoid Disconnected
    22 - No. 1 Solenoid Short Circuit
    23 - No. 2 Solenoid Disconnected
    24 - No. 2 Solenoid Short Circuit
    25 - B1 Solenoid Disconnected
    26 - B1 Solenoid Short Circuit
    41 - Throttle Sensor
    52 - Vehicle Speed Sensor
    55 - Neutral Start Switch

    Here is a fairly useful diagram of all of the positions of the automatic transmission electrical components:


    I haven't had a chance to check my transmission codes but I implore all of you to do this immediately. You can make a jumper wire with a paperclip.
    shogun, DEG95DH and Steven Stewart like this.
  3. MrJPolito

    MrJPolito Active Member

    In one of Shogun's previous posts (earlier in this thread) he links to a Japanese blog where someone tried to swap their transmission computer with a Mitsubishi one and it didn't work, so they had to repair the internal capacitors. So that probably won't work anyway.

    Would be a good idea to check the codes at this point and see if the computer will just tell you what's wrong with it.
  4. Ronso

    Ronso New Member

    Thanks for the info. I'll have to check it out when I get a chance.
  5. MrJ that is an amazing find! And quite genius using Google translate. If I can find my OBD port I will certainly try the transmission scan. I did find on my stereo rewire that fuse you mentioned was blown and the previous owner had stuck some foil from a cigarette wrapper in there to bridge the fuse. Replaced it proper but no changes for me.

    ***Update- found my diagnostic port tried to read the transmission codes. I seemingly do not have a pwr light
    Last edited: Nov 15, 2021
  6. MrJPolito

    MrJPolito Active Member

    Do you have the PWR switch? Should be a light bulb position for PWR next to the 4x4 lamp on the instrument cluster. If you have a PWR switch you should have the bulb. I'll see if I can find anything out about what to do if you don't have that.
  7. I do have a switch I have never seen the bulb lit up. I placed the jumper wire as shown and nothing lit up on the dash or anywhere else I could think to look. I did pull my engine codes just to verify the OBD connection is working. I had some stored codes reset them took a drive and nothing changed, rechecked engine codes all was clear. Tried transmission codes again and still no pwr light
  8. MrJPolito

    MrJPolito Active Member

    It's the reverse warning buzzer. False alarm, lol.

    Steven Stewart likes this.
  9. MrJPolito

    MrJPolito Active Member

    Try switching the bulb with a known good one, like from another spot on the instrument cluster.
    Steven Stewart likes this.
  10. MrJPolito

    MrJPolito Active Member

    Alright, I'm almost certain that my computer is dead. No error codes, no light blinking, nothing. Even when I unplugged the thing it acted the same.
  11. MrJPolito

    MrJPolito Active Member

    Steven, since your PMNT fuse was blown I somewhat wonder if your computer got affected by it somehow, or maybe the wiring is still wrong. What was going on with the wiring behind your radio again?

    Also, here are two pages from the manual describing how to use a multimeter to test the inputs/outputs from the wire harness entering the transmission computer (untranslated, sorry):

    IMG_20211115_233534_824.jpg IMG_20211115_233537_699.jpg

    You can either test the harnesses entering the transmission computer (difficult if the dash is not disassembled), or test the harnesses entering the engine computer (way easier, located under the center console under the radio), although I'm not sure if the car will still run if the harness is disconnected from the engine computer. You could just shove a probe in there I guess.
  12. Yeah, I could never get a light to come on either. I moved bulbs around everything still works except the PWR light.

    When I did the radio I found a loose green wire with a white stripe single female connector. It tested as a ground but when I hooked a ground from the CB radio to it it caused the reverse indicator to illuminate and the warning sound to come on. I was curious if that is supposed to hook to something with the computer dealing with the transmission somehow or was it some kind of safety feature for the factory radio.
  13. Ronso

    Ronso New Member

    I just tried to get the error codes but my pwr light wouldn't light up either.
  14. shogun

    shogun Active Member

    Ronso, please add the car details as your signature, see as example my signature. Much easier to help for the other members.
  15. MrJPolito

    MrJPolito Active Member

    I think we have bad computers. These things are so old that the solder is probably fucked in the board connections.

    I just found this blog from a Japanese guy:

    He heated his computer module to a mere 50°C (120°F) and it worked again. I'm going to take mine out and pop it into a drying oven at work that is already conveniently set to 50°C. I imagine higher is better. Plastic supposedly won't melt until 100°C (water boiling temp) so I'm not worried about the housing melting. This temp is also still not hot enough to reflow solder so I have no idea how this is supposed to work but I'll try anything at this point.
    Steven Stewart likes this.
  16. MrJPolito

    MrJPolito Active Member

    K, so basically I realize now that this "heat to 50°C and install it into your car while still warm" thing is just a way to confirm that it is indeed the capacitors in your computer that are bad. He says that his car drove better in the summer, then stopped when it got cold, so he heats up the computer to see if it does anything to correct his issues before opening it up. If you want to confirm that your capacitors are the problem, heat your computer up a bit and install it while it's warm. If it works again, your caps probably need to be replaced, which is a perfectly reasonable project for anyone willing to operate a soldering iron. If your computer still doesn't work after heating it up to 140°F, or you don't notice a difference in your transmission shifting between summer and winter, then there's something else wrong.

    My computer has some damaged wire connections on the board that I severed when I redid the capacitors a second time. It's probably fucked, so I'm probably unable to take this any further without repairing those tiny wires. I might try it, I might not. Or I'll just sell this to a farmer who doesn't need to go above 25 mph. Good luck, everyone.
  17. shogun

    shogun Active Member

  18. DEG95DH

    DEG95DH Member

    @MrJPolito , @Steven Stewart , @Ronso

    I've been reading your posts regarding your AT issues, and I need clarification. (It's possible I overlooked information.)

    When you drive your AT, and you accelerate from 0, starting in L, then switch to 2 when the engine gets loud, then switch to D when the engine gets loud again, are you saying you do NOT get any sort of gear change?

    Similarly, you decelerate from a cruising speed, starting in D, downshift to 2 once the engine gets quiet (you should hear the engine rev up again), and as the engine quiets down again, downshift to L (you should hear the engine rev up again), are you saying you do NOT get any discernible gear change?

    Granted, I've never driven my truck yet (en route), so I am only speculating that a 3-speed AT with a L-2-D gear selector has the ability to manually upshift or downshift through all forward gears.

  19. MrJPolito

    MrJPolito Active Member

    2 is the same as D, but the shift times are longer (so it'll take longer to go from 1 to 2 to 3). From what I can tell, L is shifting through first and second gear (maybe not shifting, all I known is it's a low gear), while 2 and D are perpetually in third gear.
  20. For mine starting at 0KPH with the shifter in L.... Engine revs up as I get up to around 20-25 KPH I manually shift to "2" it seems to be 3rd gear I have very little tourqe if I keep pushing the gas I can run all the way upwards of 90 KPH, if I shift into D there is no change in tourqe or engine sounds. It never downshifts automatically. If I start at 0KPH with the shifter selection on "D" as long as it's hard even ground I can start moving and run all the way up to 90 KPH and never hear a engine noise change as if the transmission has shifted. Just to clarify at 90KPH the engine is screaming as in wide open throttle it isn't just cruising along. I believe my Van only has 1st and 3rd and only shifts manually. I do have a new symptom though when it's cold (32 degrees F) and you shift from "L" to 2 it's like you smashed the breaks and will not go. Once the engine is warm it works "normal for my van" only does that when it's cold.
  21. Better said mine is the same as Mr J's "L" is 1st gear "2" and "D" are the same, I presume both are 3rd. I don't believe mine automatically shifts ever.
  22. DEG95DH

    DEG95DH Member

    Hmmmm, ok, thanks. I was looking at the table you provided elsewhere, assuming it was applicable to Toyotas with 4 speed AT. I assume 3 speed AT would have only the yellow highlighted options (or maybe D is OFF/OFF in ours?). Otherwise, why have a 2? -- especially when you also have a ECT PWR button that raises shift points?

    I guess I am suspect of a solenoid.

    I have collectively owned about 10 Lexus/Toyota vehicles, all with these PWR buttons (except for CVT models). They do raise the shift point RPMs, but if I manually gate shift them, they go through all the gears manually. For example, I almost exclusively gate shift my 5-speed AT Lexus, and it's gate is L-2-3-4-D. If I leave it in L, it stays there. But, in 2, it'll control between L-2, and so on.

    upload_2021-12-2_13-43-7.png upload_2021-12-2_13-57-29.png
    Last edited: Dec 2, 2021
  23. MrJPolito

    MrJPolito Active Member

    I have the same issue now. Truck will brake abruptly if I go from L to D when it's cold.
    Steven Stewart likes this.
  24. I still have yet to see my PWR light come on when I try to pull transmission codes.

    DEG95 makes a good point is solenoid 2 is malfunctioning in the OFF position the transmission would act exactly how it's acting. I tested mine it seemed to work fine but the PC not allowing you to pull trouble codes points more towards the transmission control module. #2 solenoid malfunction would make alot since now if the stupid computer would just tell us.
    DEG95DH likes this.
  25. DEG95DH

    DEG95DH Member

    Ok, thanks. Once I drive mine, I can contribute more. But I think I understand now what you are experiencing. (But certainly not why you are!)
  26. MrJPolito

    MrJPolito Active Member

    If your PWR button turns any indicator light on, your transmission computer is probably working. If not, I'd be worried about the computer then. It's a pretty good indicator of the computer being broken rather than a solenoid not working.
  27. DEG95DH

    DEG95DH Member

    Consistency is good!
    Steven Stewart likes this.
  28. DEG95DH

    DEG95DH Member

    If (1) AT ECM computers are notoriously bad, unavailable, and unfixable, and (2) both solenoids are working when powered, then all we need to be able to do is manipulate 3 combinations of 2 electromagnetic solenoids!

    I'll build a gaming shifter...

    ...or buy a push-button shifter!

    Just throwing out ideas at this point. If I lose 'automatic' function, but get to keep all 3 gears, I'll be content. But, losing a gear on only a 3-speed tranny will be a major problem.
  29. I really like the way you think. We could accomplish this with 1 toggle switch on solenoid #2 as a test. #2 off in low, on in second and on in third.
    Last edited: Dec 2, 2021
    DEG95DH likes this.
  30. DEG95DH

    DEG95DH Member

    I was hoping to drive mine first and provide more info. At this point, I'm all conjecture.
    Last edited: Dec 2, 2021

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