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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. MrJPolito

    MrJPolito Active Member

    In my automatic transmission 1995 Daihatsu Hijet S110P with 4wd, there is a transmission computer mounted behind the steering wheel and instrument/gauge cluster.

    As some of you might have already read, my Hijet (and others with automatic hijets) get crappy acceleration and feel like they're stuck in third gear and never change unless you go to L on the shifter. You can clean the transmission solenoids, you can replace the transmission fluid, you can replace all of the fuel system components, and the car's acceleration does not improve.

    Well, I just took out my truck's transmission control computer and drove around for a while. It performs _exactly the same_ as with the computer plugged in.

    IMG_20211014_213833_240.jpg IMG_20211014_213836_062.jpg

    It being broken would explain why my PWR button does nothing and why it never seems to shift into gears beyond third.

    What do I do with this information? How do I test if this thing is actually working? It doesn't appear to be serviceable at all, but I could pry off the backplate (and probably break it).

    Jan 12, 2022 edit:
    I believe we have solved this issue. Read the thread for more details, but you need to replace the capacitors on your transmission control computer. This fixes issues with the transmission computer not shifting on its own, and the PWR button not functioning.
    Last edited: Jan 13, 2022
    shogun likes this.
  2. shogun

    shogun Active Member

    Looks like you found the culprit. Have a capable radio/TV repair shop nearby you to have a look and repair it? cut the housing open, see link below. In the TCU usually capacitors inside get old and have to be replaced, have done that on some BMW trans control units. Also re-soldered cold solderings. Searched a bit in Japan and here is something, not exactly the same part no., but almost identical. https://www.autocar.jp/specialshop/2019/08/21/402386
    I copied the text in English, in case it shows up in Japanese for you : I saw an article about repairing an automatic computer at Daihatsu Atrai / Hijet on our blog before, and received a repair request from a maintenance shop in Gunma prefecture. The customer first consulted with a local ECU repair company , but he refused, saying, "Because it is a computer unit with resin poured in, it cannot be repaired ." The case of the unit is also non-disassembled, and even if it is repaired, it cannot be guaranteed, so it is usually refused by a specialist.However, we have devised a method to improve the solder adhesion of the parts on the board of this computer, which is difficult to solder, and have been repairing similar Aisin AT computers with the Pajero Mini and so on. Of course, we cannot guarantee it, but we offer it at a lower price than purchasing a new one, so we are working with the customer's understanding, so we have not received any complaints at this time. Hmm. When I explained such circumstances, he said, "In any case, new products are expensive and production has already ended. He sent me a broken computer. The Hijet Aisin AT computer that arrived looks exactly the same as the Pajero Mini's, but it is not compatible with the Daihatsu and Mitsubishi, and even if I attached the Pajero Mini's to the Daihatsu before, it did not work well, so the actual thing Will be repaired. When I made an incision in the computer unit that arrived, the capacitor did not seem to be punctured at first glance, but it was damaged, so I replaced it. These 5 capacitors were replaced this time. You can see how small it is compared to the 5-yen coin for comparison. It took less than 12 hours from the arrival of the repaired item to the shipment. At a later date, the other party contacted me saying, "I installed it and tried a test drive, but it was fixed!" I was very pleased.

    another one: https://minkara.carview.co.jp/userid/1493884/blog/43872960/
    It is a Hijet truck of 1993 car, but I was in trouble because of AT malfunction. The mileage is about 13000km, and the appearance is a beautiful car without rust. I just said that the AT wasn't working well, and it wasn't a good idea to switch, so when I consulted with Daihatsu Dealer in Matsumoto, I decided that there was a cause in the AT, so I made a repair that involved a little expense, such as replacing the AT. (A total of about 220,000 yen). I replaced the AT body with a rebuilt product, but I was looking for an AT ECU unit because the cause of the shift was probably the AT control computer. It was said that this AT control ECU could not be supplied because it was out of stock at Daihatsu and AISIN, the manufacturer. There was no other way than procuring used parts, so I searched for Yahoo Auctions and recycled parts stores, but I couldn't find them until recently. At the beginning of last week, Daihatsu found a second-hand AT controller ECU, so what should I do? I received a phone call saying that, and when I asked for the price, it was 25,000 yen. Well! At the demolition yard, 5,000 yen is a good place, but did you put 5,000 to 10,000 yen on the broker and 10,000 yen on the dealer? Even so, the AT has been replaced, and it is not interesting to ride an AT car that does not shift as it is, so I bought it for a large amount of 25,000 yen. It seems that it comes with a half-year warranty. For that reason, it was time to replace the AT controller today. It is an AT controller equipped with this Hijet from a new car. When I contacted Daihatsu Dealer during the replacement work today, it seems that it is an early model. The base is hardened with resin, and the base surface is completely invisible, and when you hit it with a hard tool, it looks like a lump of resin that makes a clicking sound.
    (I couldn't see the contents and I couldn't do the ballasting, so I gave up repairing it.) This is the AT controller I bought second hand. Here, the back side of the base is also visible through the gap in the metal case, and it may be possible to repair it by disassembling it. Today's inquiry revealed that this is a later compatible part. When viewed side by side, the compatible products are larger, but the mounting dimensions are the same. Although it is a replacement work, it is attached to a place that is quite difficult to do even though I am accustomed to it. First, remove only the upper half of the steering post cover, and remove the upper two bolts out of the four bolts that secure the steering shaft column. Also remove the universal joint cover on the steering shaft. Loosen the bolts that secure the lower steering shaft as much as possible. With the steering as if it were lying down, remove the upper side of the steering column cover, and then loosen the right side of the lower bolt and pull it out. This work was absolutely necessary because I could only unlock the meter wire socket through the hole in the plate that holds the steering column in place, and I've only recently noticed this. Next, remove the panel around the meter, remove the meter unit, and remove the air conditioner duct. It is finally possible to access the AT controller. You can see the white brake oil tank on the right, but there is an AT controller in the back, and it is attached in a place where it seems that there was no other place to attach it. It is in a state where it has been replaced and replaced. It's just this exchange, but it's a lot of work because it's necessary to have a ballast so far., Results, superb AT has resurrected. After a long time, and revived is crisp ran, excellent condition is the thing. Lightly, then you have to shift, manual Even if I downshifted with, it downshifted without shock. Even before replacing the AT controller ECU, it worked normally in a warm indoor environment where the heater worked, but when the room is cold and cold It is a run that is only driven by a torque converter that is fixed at 3rd speed and in a half- claw state. It  was a run similar to the light one in the 360CC era, so I was able to ride it moderately, but it still runs normally. I am satisfied with running lightly. Finally, the AT problem was solved.

    Maybe they have a used one and if you have a spare, you can risk to damage one , ask here https://autoparts.beforward.jp/search/DAIHATSU/Computers---Sensors/Computers-Transmission/
    Steven Stewart likes this.
  3. MrJPolito

    MrJPolito Active Member

    Incredible find. I'm definitely going to try replacing the capacitors. Since the current module doesn't work I'm not worried about getting a replacement before opening it up. I've done some electronics soldering before so this doesn't seem terribly daunting to me. Might be a while before I get the replacement capacitors in the mail but I'll post progress here.

    A used transmission module would be pretty expensive and there's no guarantee that it will not have the same issues, so I'm happy to try replacing the capacitors.
    Steven Stewart likes this.

  4. Please let me know how that goes may have to mail you mine .
  5. MrJPolito

    MrJPolito Active Member

    IMG_20211017_153713_605.jpg IMG_20211017_153716_582.jpg

    Cut open the transmission control computer module. Looks exactly the same as the Japanese blog post one on the inside. One out of the five capacitors wouldn't change when tested with an ohmmeter. Replacing all of them, will report back when I get the new ones in.
    dredso3, shogun and Steven Stewart like this.
  6. Got high hopes for you sir... I'm guessing the only test is to unplug mine and see if I does or does not change anything? I would expect it would not since mine isn't shifting at all anyway. I know I don't know anything about the insides of electronics. I messaged a guy in Israel that is advertising engine and transmission control modules on ebay I would much rather deal with someone that I know is rebuilding or repairing them not across the ocean. I used the numbers from your pictures for a P/N I'll let you know what he says Is there any particular trade I could check with that may know what to do with these? I read TV repair shop but I couldn't imagine anyone that would take on something like this without having some background knowledge of our situation. FYI I'm not kidding if this works out for you I'll hire you.
  7. MrJPolito

    MrJPolito Active Member

    Yeah, try unplugging it and seeing if there is a change in the way it drives. Mine didn't change at all. You can either remove the module by taking out two bolts holding the bracket onto the frame behind the dashboard, or use a small screwdriver to unclip the plastic box from the bracket. Might need someone with small hands to reach back there. I took out the instrument cluster but didn't have to remove the whole dashboard or anything crazy like that. Just a few screws.

    If this works, I'd happily do it for the cost of parts and shipping things back and forth. Venmo makes this sort of thing easy nowadays. Buying the capacitors was under $4 and shipping is only $6 via USPS. Caps have been ordered from Digi-Key and will arrive in a few days. Will let you know. It really sucks that we bought these things and didn't notice that they don't work right until way afterwards.
  8. Well unfortunately the guy I bought mine from says he's been driving this one like it is for 5yrs, I don't know how. I thought maybe I could figure it out I knew it wasn't slipping so figured it would be any easy fix. I have figured several things about my van out since I bought it Friday before last (oct 8th) absolutely love this van. I just gotta get the cold start issue, 2nd gear thing out of the way. Then I'm going to weld the rear end up, tint the windows, rewire all the non factory accessories add some "cup" holders and I'll be ready for the road. I cannot wait!
  9. MrJPolito

    MrJPolito Active Member

    Alright, so I put new capacitors in but it didn't change anything. It's impossible to tell if the computer is the source of the problem. I'm not really satisfied with the quality of my solder joints so I've ordered a new soldering iron station that doesn't suck balls like my current one. It wasn't getting hot enough and the solder joints were popping off too easily.

    In the meantime I'm going to try to trace some of the transmission control wires and make sure nothing is obviously severed, and maybe clean some electrical connections.

    Does anyone know if a bad speed sensor would cause the transmission computer to enter failsafe mode? That's one of the components I've traced to the transmission computer so far.
    Steven Stewart likes this.
  10. The technical data sheet from Toyota that I believe was posted on your previous thread about the power switch or bull mode discussed the throttle position sensor and speed sensor in depth. I'm sure it's not exactly the same but probably has a similar function. Have you tried to consult with a transmission person? I've got a good acquaintance that owns the best transmission shop around I think I may swing by and talk with him a bit. I'm not sure if his computer will attach and read our type vehicle or not but I guess it can't hurt to ask.
    Last edited: Oct 22, 2021
  11. MrJPolito

    MrJPolito Active Member

    I live in the middle of a wheat field so there's only one transmission shop the next town over, and they didn't reply to my email about sourcing a solenoid. Maybe I'll call them instead, just for advice on how this works. I'm going to remove whatever sensors I can see sticking out of the transmission or plugged into this wire harness and test them. There are at least two that I can see on top of the transmission.

    Might also see if this DIAGNOSTIC port is OBDI and if it can be read by any of the loaner code readers they have at O'Reilly. I don't have an engine light though, so I don't know if there would be any useful info. (The bulb works and lights up with the key in the accessory position, so I know it works fine)
  12. I donno about OBD1 reading transmission codes. Use to you could put a jumper (paperclip) and the CEL would flash the pending codes that could be looked up. If I remember correctly it's really only emissions stuff. I'll check with a friend on the ability to read transmission codes and report back.
  13. shogun

    shogun Active Member

    this OBDI reading is mainly for the engine/emission, usually it does not include in depth fault code reading of other parts like trans control module etc.
    If you cannot fix the module, contact one of the ECU/electronic parts repair shops. As I also own some old BMW, I know from US forums that many send their modules to Programa Inc, which is concentrating on European cars, but maybe you contact them if they can check it https://www.programainc.com/default.aspx
    Last edited: Oct 24, 2021
    Steven Stewart likes this.
  14. Put my van to the test today first day on the hunting club. It did good no winch needed today a few issues came up though. 1- springs are to soft... easy enough, plenty of info on here to correct this one. 2- sidehilling (bout flipped over) - wheel spacers may help but it kinda is what it is. 3 - gears... I've got 25s so do I need to swap for a lower gear ratio or shorter tires. Does anyone have any ideas? I just plum don't have enough umph to spin the 25s over.... Edited 10/25/21 I wrote the first round under the influence, it made no sense when I re-read it.. sorry folks
    Last edited: Oct 25, 2021
  15. MrJPolito

    MrJPolito Active Member

    Took out two computer modules from under the center console. There are two stacked on top of each other. Here is the top one:

    IMG_20211025_011225_463.jpg IMG_20211025_011220_345.jpg IMG_20211025_011222_540.jpg

    Board is pristine in this. Absolutely beautiful.

    But the second (lower) module is full of horrible corrosion:

    IMG_20211025_011217_037.jpg received_395799492048629.jpeg received_260133479460512.jpeg received_875621309756539.jpeg

    Good computer appears to be the Engine Control Unit and the bad looking one is a power steering control board. No idea if this would cause the transmission to not work correctly. Might try to trace wires again and see if this thing is what normally sends power to the transmission control module or if it has any attachments there. Would make sense if it's not working from the corroded crap. I can replace the caps and clean it up but I don't know if that'll be enough. New soldering iron coming tomorrow. We'll see I guess.
    Last edited: Oct 25, 2021
    Steven Stewart likes this.
  16. Probably a silly question... Do you have power at the transmission control module? I need to start digging into mine but I was going to start at the fuse block I'm curious if any of the important ones are blown.
  17. MrJPolito

    MrJPolito Active Member

    Haven't checked yet lol

    I don't know if there even is a fuse for the transmission computer. It's not very obvious in the way the circuits are labeled. I don't have any blown fuses though, unless I'm straight up missing a fuse.

    I'll put the computer modules back in the car and check the wire harness at the transmission computer for voltage real quick later today.
    Steven Stewart likes this.
  18. So I played with my van today, checked all my fuses only had one that was blown none are missing( whatever PMNT is) I have dome lights now, but still nothing changed with the transmission. I unplugged the transmission control module and drove around and it was not one single bit different than driving while it is plugged up. I could not test the wires to the control module without removing some more stuff from the dash so I have no clue if anything is talking to the module, we are taking the van truck or treating tonight so I didn't want to get to deep into it. I did find the PWR button was unplugged and the wire going to some kind of alarm assuming door warning is unplugged.
  19. MrJPolito

    MrJPolito Active Member

    I checked the voltage on the capacitors I installed in the transmission control computer and they were getting power. So the transmission computer is getting power for sure.

    Also replaced all of the capacitors on the engine control computer and power steering computer, and cleaned up all the corrosion on the power steering computer. Absolutely no difference in engine shifting or anything.

    PWR button still doesn't do anything.

    I'm still not entirely sure if it's supposed to shift better than this or if it's just the nature of how the car was designed. Regardless, I'm getting a Mitsubishi Minicab soon (still needs to board a ship) and I'll be able to compare the engine power and shifting since it's also automatic transmission.

    No idea what else to check at this point with the hijet.
    Steven Stewart likes this.
  20. MrJPolito

    MrJPolito Active Member

    I took apart the transmission shift position sensor today and cleaned it up. Absolutely no idea if it's problematic but it was pretty gross in there and I figured it probably gets a lot of dirt and water from the undercarriage. Only a few philips head screws hold it together. There are two tiny springs in there, make sure you don't lose them.

    PXL_20211004_002503538~2.jpg IMG_20211102_215655_215.jpg IMG_20211102_215644_326.jpg

    It's just a lever with two copper contacts on it that swipes back and forth depending on the shifter position. Mine had a bunch of copper particulate smeared into the grease which might be causing shorting. Just to be safe I scooped the grease out with a tiny screwdriver, degreased the whole thing, sonicated it with cleaning solution for half an hour, then put it into a 50°C drying oven for three hours. Then I repacked it with dielectric grease and put it back together.

    IMG_20211102_215721_997.jpg IMG_20211102_215726_290.jpg

    Also put some industrial silicone around the outside edge just in case the gasket is crap after 25 years. The sonicator really cleaned up the electrical contacts and I was very impressed with how it looks.

    Will reinstall tomorrow once the silicone has had more time to cure and will let you know if it changes anything about the transmission not working correctly.
    Steven Stewart likes this.
  21. shogun

    shogun Active Member

    Good idea to clean also that.
    shift position sensor is very important, if the trans computer does not get the right signal from there, trans goes in limp mode, I know that from my 1989 BMW E32 750, here some posts with pics just for info how important that is on the BMW
    shift selector switch contacts. http://www.bimmerboard.com/forums/posts/744694/
    Excerpt from Bentley's repair manual BMW E32 7 series : "A faulty gear position/start disable switch may cause transmission shifting problems and erratic transmission operation" http://www.nmia.com/~dgnrg/page_13.htm
    Steven Stewart likes this.
  22. MrJPolito

    MrJPolito Active Member

    Alright, that didn't change anything. Changing the title of the thread since this is more about troubleshooting in general than the transmission control computer at this point.

    All that I can think of now is to clean the air intake and make sure the throttle position sensor is working. After that I'm all out of ideas. Ready to sell this thing and never look back.
    Steven Stewart likes this.
  23. You have definitely been thorough stuff I wouldn't have thought of. If that original paper from Toyota that you had or got from about 2 threads back is applicable to our vans auto transmission you are barking up the right trees to find the component that is failing you. I feel like if it is ever reviled it will be a simple solution (like a light bulb being out) I know you have been through that as well.

    Does anyone have any idea if the 2nd gear slips or goes out does the vehicle somehow disable that option? Meaning all this trial and error testing and repair is null because the transmission is bad and the truck knows it?
    Last edited: Nov 3, 2021
  24. MrJPolito

    MrJPolito Active Member

    I have no idea about the radio wiring but it sounds like it's probably unrelated to your transmission problems and might be a good idea to post a new thread for that.

    Regarding the diagnostics port on the Hijet S110P, it looks identical to the Toyota OBD1 port. According to the attached document, it's possible to bridge two of the terminals with a jumper wire to retrieve any engine codes as indicated by the engine light flashing a certain number of times. It is also possible to clear the codes by removing the 15A EFI fuse for a certain amount of time. See photo of diagnostic port and Toyota port diagram below.

    Screenshot_20211104-015334~2.png IMG_20211104_015300_096.jpg

    I'll try it tomorrow but I just removed my ignition coil for replacement and my throttle body for cleaning, so I can't actually try to drive around. Should be able to check if there are codes though, even if it's not driving. Maybe try to check your codes or reset them too Steven.

    You might also be able to borrow a loaner Toyota OBD1 tool from an auto parts store.

    (Read attached document for more details about checking engine codes with a Toyota OBD1 diagnostics port)

    Attached Files:

    Steven Stewart likes this.
  25. Ronso

    Ronso New Member

    I just picked up my 1995 hijet and it is having the same transmission issue. Have you had any luck finding the cause? After I took my gauge cluster out I noticed a little denso chip on the back of the cluster that was covering "a/t". I was curious if this could be doing something.

    Attached Files:

  26. I have not. MrJ has been deep into this issue he hasn't posted in a while but I am assuming he hasn't got his figured out either he has been very thorough and posted a lot of information on various components. I haven't seen that part untill now. The biggest improvement I've had thanks to MrJ's post was cleaning my solenoids, filter and changing the fluid in my transmission. I still have no automatic shifting but had a huge improvement in performance (still not impressive). I wish we could figure out our common denominator besides no shifting. Mine is "idle hunting" poor fuel economy seemingly poor performance and I am after that issue I believe to be related to temperature sensor.
  27. MrJPolito

    MrJPolito Active Member

    Ronso: I tried looking up what that module could be and can find literally zero info. Mine has the same thing on the instrument cluster. I can only assume it has something to do with one of the instruments but I don't know if it's vital for transmission function. My brothers work in the auto industry and they haven't seen that either. None of my friends who work on circuit boards could identify it either.

    Regarding where I left off previously, I checked my engine codes and don't have any. I definitely did have some when I unplugged a few sensors (throttle and its sensors was disconnected) but they've since cleared, so I know that it works.

    Summary of everything that I've done so far:

    - drained and replaced transmission fluid and cleaned and fixed stuck solenoids
    - cleaned fuel injectors and installed new fuel filter
    - installed new ignition coil and spark plugs
    - installed new distributor cap/rotor
    - replaced all of the capacitors in the transmission computer, engine computer, and power steering computer
    - cleaned out and re-greased the transmission position sensor
    - disassembled and completely cleaned the throttle body and its associated sensors (coolant temp sensor, throttle position sensor, pressure sensor)
    - replaced leaking oil seal on transfer case and drained/replaced oil with 75w90
    - added half a bottle of Lucas oil "transmission fix" to the transmission (drained some trans fluid before adding so that it wasn't overfilled)

    Out of all of these, the most noticeable change to the transmission and overall power appeared after the bullet points highlighted in bold. But the power is still lacking, and I still can't tell if the transmission is even shifting.

    After I replaced my ignition coil with a new one, I'm noticing that the car stalls when the engine is cold and I try to start it. It'll start running if I give it some gas and it eventually starts automatically revving the engine on its own, and it no longer stalls. Also, the car now struggles to move in drive when the engine is cold. I have to switch to L just to move forward. Once the engine is warm it goes away. Not sure what that's about, but it matches Steven's problem now.

    I was looking up more details on these transmissions and I'm starting to think that this is just the nature of a 3-speed automatic transmission from 1995. I originally thought we might have 4 or 5 speeds, but lolno. Just 3. Maybe these just suck and the computers in this era aren't good at figuring out when to up/downshift. I would like to see someone else with an automatic kei truck from the same year or earlier tell us otherwise.
    DEG95DH and Steven Stewart like this.
  28. MrJPolito

    MrJPolito Active Member

    It's also entirely possible that the little pathways inside the transmission maze are clogged and we're not getting any shifting when the solenoids get triggered. I don't think you'd get engine codes for that. This possibility is why I decided to add the Lucas Oil Transmission Fix to my transmission and see what happens. No idea if it's doing anything useful yet. When I added it, some of my rough shifting issues definitely stopped.
    Steven Stewart likes this.
  29. Ronso

    Ronso New Member

    I also have 1995 Mitsubishi minicab automatic and it shifts normally 1-2-3 while in drive. Unfortunately the transmission computer is a different style so I couldn't swap to try. In my research I've found the mitsu pajero mini transmission computer looks very similar to the Daihatsu. I wish I knew someone with one to try swapping before buying one.
  30. Ronso

    Ronso New Member

    I also found in a Mitsubishi forum that some people have luck heating the transmission computer with a hairdryer

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