1993 honda accord mysterious D4 Solid now D4 blinks
My car is a honda 1993 accord auto transmission LX sedan.

For a while I have been a having a D4 light issue on my car. I will brief the history on this best of my memory. But I need to obtain one record and that is when I got the transmission control unit (TCU) repaired for original TCU in the car.

Okay what first started happening was this. Before I tried to get a TCU repaired. I drive the car. When I go to park the car. I shift into park. The D4 stays highlighted as I go to park. Now a symptom of this problem is that. When I stop at a stop sign. And I go from a complete stop,
it doesn't accelerate the best that it can when I start going. To explain this a little better, I go to park my car at home. The driveway is at slight incline, now in this weird state. To get up the drive way, I have to accelerate the car. But if this error of the D4 light isn't highlighted. You don't even have to press on the gas pedal and the car goes up automatically. That is the best I can explain it. Because someone that hasn't ever drove my car, probably wont notice. Also it drives quite well when it's accelerated. Maybe there was one rare hickup.

Now to solve this problem. I disconnect the battery for 10 to 20 minutes. And then I reconnect the battery. My theory is that it resets the computers in the car. Now it goes back to normal with the D4 light not going into a solid state. You know it's 100% working perfect because as I said before I can drive up my drive way without even putting my foot on the accelerator. Now it may last 3 to 4 days. And some occasion 2 weeks. Before it goes back to the D4 error solid state.

Now at some point. I don't have the current record on when I did this but. I don't know how many years ago it was probably some time I replaced a TCU, and I couldn't remember what the issue was (2013?). But I got another TCU from a junk yard. So I replaced my original TCU with the junk yard TCU found in another honda accord. The problem of that TCU was fixed doing that. Anyways, I kept the original TCU from the honda accord. Okay anyways fast forward to 2021 at some point I wanted to replace the TCU again, because of this issue I'm having now that I'm currently explaining. Except to continually want to use the car. I didn't use the current TCU, I used the original one (to get repaired). I used this car place that repairs TCUs through ebay. The guy wanted me to explain what was wrong with that old original TCU. In which I couldn't remember. The only thing I could tell him it's a bad transistor or a bad cap in it. Which I physically saw. It was a judgement call. Plus, I wanted to use the car at the current time. I'm not sure it would be a good idea to put a old TCU in from 2013 and use it that way. Then send the current TCU with issues I'm having currently.

Anyways, this is were my memory gets a little fuzzy on what's going on. I get the part back from the repair shop. Of course it has a warranty sticker on it. Don't remove. Anyways, I install it. And I can't remember what issues came up with it. But it seemed like the new issue became the issue of a now D4 blinking light. I can't remember if the D4 light started blinking right after or it went from D4 solid state to a D4 blinking light. Anyways, I didn't really at the time check the OBD scanner to see if there was a diagnostic of the TCU. But I had someone suggest to me to replace the shift solenoid and the lock solenoid. I bought it in March 23, 2022. Maybe it was 2 or 3 days later that both were replaced. Now I can't even remember that much well. I remember noticing it didn't fix the issue.

Anyways, I just kept driving the car at this point, because I need to use it. I know I'm kind of procrastinating the issue. Anyways, I don't know if it was June of 2022 or July 2022. I decided to try the OBD scanner by putting a paper clip in the cable that is under glove compartment. That brings up. 7. Shift Solenoid A circuit open or shorted. So I think to myself. Which one is the shift solenoid. I had to do some research on that as well. I figured out that the one above the shift solenoid is the Lock solenoid. So the one below the lock solenoid is the shift solenoid. Okay, so I decided to disconnect the battery. Disconnect the shift solenoid power connector. Maybe look to see if it's dirty or what not. See if anything happens. Nothing changes. Same error, and I give up. And I procrastinate some more.

Anyways, October comes around. I decided maybe I should replace the shift solenoid. Of course I forget which one it is again. Whatever, I find some chart on the internet to show me which one it is. I order this time a re manufactured part shift solenoid. It's a long shot because I know the shift solenoid part I replaced was a new one. Anyways, new shift solenoid comes into the mail. As I'm noticing I'm taking off the old one. One of the wires seems to be stuck near the top bolt. For some reason, I put a bolt through the wire. So I ultimately came to the conclusion that's what caused the short. And now everything makes sense. So I get the shift solenoid out, sure enough the wires have been damaged a little bit, you can see the wires sticking out of it.

Okay after I put the new solenoid the one I just ordered. I have everything installed. Everything bolted on. I put the OBD scanner on. No error code. That was only because I reset the battery and have not drove it yet. Now I started driving it again, and once again the D4 light is blinking. I of course park the car. Hook up the paper clip. And of course yet again. I get 7 blinks on the TCU code. And it comes to the Shift Solenoid A circuit open or shorted.

Now I don't know what to do at this point. I do have a theory it could still be the TCU (Transmission control unit). I can't necessarily take my car to a mechanic. There isn't enough symptoms of the transmission itself to say that it is bad. Another words, I can't have them say oh your transmission is bad. Well, I have been driving the car with this D4 light issue for a while. It's very hard to explain all of this to mechanic. I have to get more specific. I think it's a computer issue. I don't know. I find it strange that it would reset with a battery disconnect. But now resetting the computer does not change the error. I'm not sure if I can have another mechanic look at the TCU or test it? Or just keep driving it or what I should do. Is there any theories on what I should do here? I might need a specialist that knows hondas. I really cant trust the dealers. Even if I did take it to a specialist. I'm not sure if they can be 100% positive on what the problem is. I'm kind of leaning into doing something with the TCU. Find that other TCU that I had, see what that does when I put it in there. I don't know where I put it. Or just buying a new TCU. Maybe the mistake I made was having that TCU sent in for repairs. But other than that, do you guys have any other theories? I just have a theory that if it truly was a bad transmission, fixing a D4 solid would not be able to be fixed by a battery disconnect. If that transmission is really bad than more major symptoms occur. But I'm not a transmission expert. And I was told a bad transmission can cause sensor errors. The point is I can't just take out a transmission and have it analyzed. Not for free anyways. Unless mechanics have a special tool to test transmissions and look at its inner workings with it still in the car.

In the mean time when you are trying to come up with theories. I need to pull up that ebay record of when I sent that original TCU to the repair shop. I also must find that other TCU. I don't know what I did with it. I just want to get the time frame of when and how long have I had this issue.

 

If the transmission shifts and doesn't slip, then the transmission is likely ok. The code 7 is an electrical fault, so likely not a problem with the internals of the transmission.

My best guess is the direct short to ground caused damage to the TCU, because the TCU sends power to the shift solenoid. The problem can also be the wiring is damaged along the way too. Can you post a picture of the damaged wires?

 

Yes, I will show the damage that bolt did to the wire.





Now the TCU I'm going to show you (in a picture) isn't the one currently in the car. Which is allegedly causing the D4 light to blink. This TCU is the one that is allegedly causing the D4 solid light (in the picture). This was not repaired. The one that is currently in the car was sent out for a repair on Nov 3, 2021. So some where around in November 2021 I had the original TCU repaired and fixed which did not fix the issue. The TCU that is currently in the car could be damaged. Which I haven't had to a chance to taken out of the car. So maybe the Shift solenoid did damage to the TCU. But even before I installed the shift solenoid. That fixed TCU didn't repair the problem. Anyways, look at this current TCU and see if you can find an issue with it. I cannot.





It would seem the D4 blinking really started after the shift and lock solenoid was replaced. I can't remember if it started right away. But those solenoids were replaced with new ones some time in late March 2022. I thought about what you said about the actual connection going into the shift solenoid connector. And if that wiring is bad. I thought I could maybe interchange the lock solenoid connector with the shift solenoid connector and see if it was put up the new error on the lock solenoid. Well, the connectors are different so I couldn't do that. I think I might try to put the TCU that is pictured currently and try putting that in to see if anything changes. As you said the transmission shifts good and doesn't slip. And the symptoms of a bad transmission are way more extreme. I know if I can't fix that TCU or get a new TCU to resolve the problem. Then I am in a real mystery here.

Update: Interesting information. The guy that repaired my TCU does have a good reputation. I found another forum post where another guy used him (Same name, same company, same phone number) and he got successful results. He has got a phone number. Maybe I can give him a phone call. Although, no email to contact him. I would refer him to this post. To see if I can get his opinion on the matter. Although, I could contact him through Ebay. Correction I found his email.

Update: Now when you said that a bad shift solenoid could cause damage to a TCU. I looked at more information regarding this. Somebody said the same thing as well. That when a shift solenoid fails it causes the TCU to fail (he claims to repair them). And I have been driving around my car since March 2022 to Oct 2022. Yeah, that TCU could be very damaged. I really need to open that thing up. And I can forget the warranty on that TCU. Because of that huge mistake I made. Also, I now found some information that it's not a good idea to take a TCU out of a junkyard. Because that TCU has many miles on it, and it is on it's way to failure. It will be good to get a rebuilt one. It was a good decision to have the TCU rebuilt. My next step is to get at that original TCU. Get it out and take the warranty (now void) sticker off. And look at it. I sure hope a bad TCU can't damage the solenoids. Also, I need to get that TCU the one that is pictured installed. To truly see if the D4 blinking issue error code 7 will go away. But the D4 solid issue might return. If my theory is correct that is what will happen.

Although there is one thing that doesn't make sense. When I got that original TCU fixed in Nov 2021 and installed it. It never really fixed the Solid D4 light problem. And if I'm assuming that those original solenoids weren't bad. Then I'm back at square one. It will of course will go back to the original D4 solid light problem. Unless, if I get extremely lucky and it fixes both problems. If the TCU in the picture wasn't actually damaged and it was the original solenoids that were causing the malfunction. Also, I want to make something known so you don't get confused. When I say the original D4 solid light problem. I mean when you drive and you go to park. You will notice the D4 light is still highlighted. Or in reverse, the D4 light is still highlighted. Also, I must add the fact the computer will be reset. So in theory the D4 light solid problem will not show right away. But it will come back in 2 to 3 days or maybe 1 week or 2 week. I know this all sounds very strange. And I didn't expect this weird issue to get so complicated.

 

I thought the 93 accord TCU used the S (sport mode) light to flash codes and not the D4. Does you car have a S light?

What are the first 8 digits of you VIN?

 

No, my car doesn't have a S light. I kind of looked that up. The indicator light would be under the temperature gauge for those cars that have it. I'm not really sure on the history of sports mode. I just know mine doesn't have it. Maybe they sold 1990-1993 honda accords with and without the sports mode. Interesting that it's the first I heard of it.

I was going to really try to install that other TCU, but I ran out of time today. Also now that you mentioned it (sports mode) I found another video where a guy claims him trying to fix his TCU didn't end up working for him. So he recommended buying another used one or a new one.
He did mention it was maybe because his soldering skills weren't the best. I'm thinking it would be better to get another used TCU. He mentioned if I don't have the honda accord with the sports shift feature than I don't have to worry too much about exact model numbers. He also was getting solenoid codes on his. And it was all fixed by another used TCU. Not fixed TCU.

Tower H
Update! This ended up not working...don't waste your time doing this, go get another Transmisson Contril Unit (TCU) from the junkyard or buy a new one. If you don't have Sport shift the model numbers don't matter, trust me

TL Nino

5 years ago
Jonathan H Is the D4 light always a tcu problem ? Been reading around saying it has something to do with the solenoid



Tower H
5 years ago
AccessDenied Dude. Trust me, its your TCU. I went to the junk yard and wasted soooo much time getting solenoids because I was getting codes that it was my solenoids...didn't work. Everything worked fine soon as I got a working TCU...same with my Dad's car- 91 Accord - all these mechanics were telling him that his tranny was shot, and I got him a new TCU and it worked like a charm. Trust me, get a TCU.

4

TL Nino

5 years ago
@Jonathan H Was your dad's car having the same symptoms such as not shifting out of park and stuff..My car doesn't have any problems getting into gears either

 

Update. There was a change. I took out my original TCU, The one I have been using. And yep there is a bad transistor, And you can even see a leak under it.
So now I decided to swap the one that I showed in the picture in this thread, the one that I never repaired. I put it in there. I turn the key. And the P and D light up. D lights up for 3 seconds and goes away. I put it in D4 and yes there is no longer a blinking D4. I stop the car, and accelerate, I don't see much difference. I stop the car and put it in P. And the D4 light has not stayed solid. When I pull the in the drive way, It still needed acceleration. I thought that was unusual, because if it isn't in it's solid D4 solid state it wont do that. You can just not press the gas pedal and it will go up a slight incline.

So anyways, I went to check to see if the Code 7 is still there. Nope. Now we got a new code. It's code 15-Kick down switch circuit shorted. So I was correct that it was the TCU that was causing the blinking D4 light and if I swapped with the other one I would get the D4 solid again. But D4 solid comes maybe after 3 to 4 days or after resting the computer. So it will come again. The only thing I was incorrect was the slight barely noticeable acceleration after stop and slight incline. That usually only appears when D4 solid appears. And the new Code 15. I did a little research and it appears Code 15 could be a sign of a bad TCU. And of course I never got the TCU repaired for one that is in there right now.

And you know what looking at the original TCU helped me compare it to the one that's pictured in this thread. I can clearly see leaks near RM1 near the middle, towards the right.

I guess at this point. I will go ahead and order a used TCU. Possibly a refurbished TCU. And cross my fingers.


Update: I just took my car on a 35 mph street. And it wouldn't accelerate past 30. It just kept on revving up. Luckily, I wasn't too far from my house. And I turned onto a 25mph street. And it wouldn't really go past 25 mph. Tomorrow I will swap my TCU again with the other one. To see if it can at least run properly with that one. I really didn't expect this at all. On the other hand, people with bad TCUs have experienced this problem. I will just have to order another TCU. And hope I can use the other one that D4 blinking one. And hopefully it wont have a accelerating issue. I don't want to get into the mind frame yet that this is a bad transmission.

Update: I swapped back to the original TCU. I went back to the D4 light blinks. Luckily, I took it out on a 35mph zone. And it accelerates just fine now. It's still damaged but at least it can move. I will be buying another TCU. I have some good options. I will report back if that finally solves the issue.

 

Update: I tried the used TCU that I got in the mail. It is giving the same problem as the junk yard TCU. It wont go above 25 mph. And as usual I had someone behind me that wouldn't pass me on 25mph zone. I was like why don't you pass me!? I was going 20mph to avoid revving the car up too loudly. He or she tail gated me the whole way. He or she only then decided to pass me as I was turning right. He or she couldn't wait for that slight delay to turn. But he or she was patient enough to tail gate and not pass me until I turned. What is wrong with people?

Anyways, I got code 15 on the TCU that I got in the mail. It's related to NM sensor. Which is related to the "NC/NM speed sensor, code 9/15"

If you google: "NC/NM speed sensor, code 9/15" click on the link techauto tripod transmission website and scroll down. Since it gave this fault on two different TCUs. It would be a good idea for me to troubleshoot these two sensors and or replace. This website has some good information on how these ATs work, and the solenoids,

It is weird that the original TCU even though it has a bad transistor. It wont pull up this code. By the way there appears some damage near R42 and R41 on the TCU that I got in the mail. The transistors doesn't appear to be burnt themselves. But there seem to be some blackness on the chip board itself. Near the leads.

I'll check out the NC/NM speed sensors. It says "The NM or NC speed sensor (code 9) should be within 400-600 Ohms at 20-degrees C. If they are not within spec replace them." Yeah, I have no idea how to check that. And It's not even 68F degrees outside to even check it.
"If they are within spec check for a possible short to ground but first unplug the harnesses at the TCU." --- I will check this. It might be a good idea to replace both these sensors just in case. Depending on how cheap they are.

What is making this whole process difficult is:
A bad TCU can gave bad or false TCU codes.

So if I assume that this is good TCU (which apparently it's not) then maybe I could assume that TCU code 15 is a real code. And not a false reading because of a bad TCU. But if it's another bad TCU than I could assume it's giving out a false reading. But a bad shift solenoid or lock solenoid will give out a bad reading to a bad TCU? Will a bad NM or NC speed sensor not give out a reading to the original TCU? Should it not give a reading out to all TCUs regardless if their bad?


Update: It's really hard to find parts for these sensors. It took me a while to figure out that it is this:

9
Countershaft Speed Sensor (NC) signal fault

15
Mainshaft Speed Sensor (NM) signal fault

Because if you type the initials in NM sensor. You wont find anything! THANKS! I found a speed sensor. Seems a little pricey for something small. But it's not indicating if it's the mainshaft speed sensor or the countershaft speed sensor. The part does look like the one on the graph. Interestingly enough. Nobody wanted to ever snap a picture where it is on the transmission on the entire history of the internet of honda related forums. THANKS! And thanks for it to be so pricey for a sensor! If it is actually the sensor. THANKS!

This is all I have to go off of! This tiny innny bitty 10by10 pixel low resolution chart:





Any help would be appreciated if you guys find these parts and understand them. I think maybe the NM Mainshaft Speed Sensor is labeled as a input speed sensor. And the NC Countershaft Speed Sensor is labeled as a output. Something is odd, when I compared pictures of the input and output Honda accord speed sensors. The power connector pieces look exactly the same. Why aren't they labeling them as the NM Mainshaft Speed Sensor or the NC Countershaft Speed Sensor? Although, I did see one named shaft. Well, they are both named shafts........

Update I did find some useful information to get my part if I want. It's still high priced. The confusion lies in they sell speed sensors for A/T transmission for Honda Accords 1990-1993, and they label them is input or output. But to skip that confusion. I wont trust that part. I found part numbers at hondaparts. Here is a little graph.




I do have reason to believe that TCU code. 15. Mainshaft Speed Sensor (NM) signal fault = is the input. And the 9. Countershaft Speed Sensor (NC) signal fault = is the output
Because some parts will be labeled Automatic Transmission Speed Sensor Input for Honda accord 1990 - 1993. My guess is based on a amazon fit confirmed fit claiming a part number from hondaparts is input. And this amazon confirmed fit also claims that the part number doesn't fit my year accord. But honda parts claims that it does. So I don't know if I trust amazon confirmed fit guide.


Update: I found the "9. Countershaft Speed Sensor (NC) signal fault " in my car. I had to remove the car battery. Then I removed the plastic battery holder under the car battery. Then I saw it. To get at the 15. Mainshaft Speed Sensor (NM) signal fault. I probably need to remove the cabin air filter. I took pictures but it got dark outside. I'll take some more. What helped me find it was actually looking at high quality pictures of the honda accord transmission 1990-1997. All four sides.

I'll post pictures later.

 

My 92 accord 4 Dr Automatic is experiencing EXACTLY the same issues!!
When the D4 Is solid no matter which other gear I place it in, The gears do not work correctly. [*to get up your driveway, have you tried 1st gear?!?)
This is one of the most exasperating issues I've ever seen because as you said, a faulty TCU can certainly give faulty readings. EVEN A transmissional specialist can't help because there are no (flashing) codes!!!
At the end of each thread somebody suggests replacing the TCU duh - BUT I only saw one where that actually fixed the issue... & 30 where it doesn't. Plus it's not like changing a light bulb, it's a very expensive and time consuming test fix.
*** HERE ARE A FEW OF MY BEST TRICKS with a few of my own modifications.
* 1st remove the 7. 5 backup fuse in the corner of the fuse Box under the hood;
* turn the key on to position 2 /Aux but DON'T roll it over (Though it won't hurt anything if you accidentally do). You should see the fuel pump light AND the D4 light turn off as the tcu/ecu/wtf circuit resets!!!!
* now WITHOUT turning the key off!, replace the fuse & cover and start your car. If you're going to drive it, from experience i found it's a good idea to also close your hood. ONLY PARK should be now lit!! Ain't that a HOOT!!? Yeehaw. Gears should work with no D4 solid and it will last... until you turn your car off again. USUALLY.

HOWEVER... Though I've been doing this everytime I start my car 6 months now,... It's snowing and rainy and the trick doesn't work anymore eventually this happens with all the tricks. Now what on Honda's Earth is causing this cuz tricks are only gonna last so long
SOMEONE PLEASE take it from here and tell the hundreds of us how to SOLVE this once and for all, thank you.

 

Okay I finally got at those sensors. The Mainshaft Speed Sensor (NM) TCU code 15. I will kind of give any info that I got just because I couldn't really find this information on the internet.

You take the front right tire off. Once you got this tire off. You will see the transmission. It's literally right there! The sensor and the bolt that holds it on. You don't have to worry about this bolt breaking off. Or spray WD40 on this bolt. It's in the transmission and its clean. Just use a 12 point 10 mm wrench. You wont have enough space to use a standard socket.



10 mm, 12 point wrench to remove. Mainshaft Speed Sensor NM. Take the front right tire off.



Next after you get the bolt off. You want to just twist the sensor left and right. Back and forth. And eventually it will come out. Once the sensor is out, you will notice there is a O-ring on it. Check to see if it's good. Okay after that, you open up the hood of the car. And you might have to take the air cabin filter off. It's really easy. You might not, I had to take mine off to look for the NM sensor since I didn't have a proper guide on the internet. I had too many false leads on where to find it. But, anyways you follow that short wiring from the speed sensor. Up to the point where you find its power connector from the wiring harness. This is where I got into some trouble.

My sensor was stuck on a metal bracket that holds that connection in place. There is a small slot on the sensor that goes into this metal piece on the car. If it's stuck on there, it's nearly impossible to unplug that power connector. I tried WD40. I tried putting a c-clamp on the little notch. That clip that you are suppose to press down. So you can disconnect it. Nothing will work if it's rusted in there. I tried using a flat head to see if I kind of loosen it and wiggle it out. Nothing, it wouldn't budge.

So finally what I did was. I decided to cut that plastic slot that holds that metal bracket in. It's not a ground or anything for the wires. You wont be cutting the wires or actually breaking the speed sensors connection in itself. I'll show a picture. I should have done a better job of it. You don't need to break the whole entire thing. You just need to use a small cutting tool. Just to free up one side. My dremel cutting wheel wasn't working good. I just took a small cutting tool from a pocket knife.

I disconnected the Countershaft Speed Sensor (NC) power connector. The NC Speed Sensor is also there under the tire. It's just towards the right. I didn't bother taking it off. You can see it from the top if you remove the car battery and the car battery's plastic bottom piece. I had to do the same with this connector as well.



Countershaft Speed Sensor (NC) power connector


Alright, after this I decided to test the ohms on the Mainshaft Speed Sensor NM. I plugged the black probe into the com port. I plugged the red probe into the VmA port. I set the multimeter to 2k. The ohms dialogue. The horseshoe symbol. I got 480 ohms. Which appears to be in range. Next I wanted to test the ground to short on the power connector that hooks up to the mainshaft speed sensor. Believe it or not it took me a while to figure this out. All you had to do was hook up the car battery. And you have to turn the key to the start position or it wont send out volt signals. I had finally figured it out when I watched a youtube video of someone testing out another speed sensor. I also unhooked the NC speed sensor, the shift solenoid sensor as well. With the digital meter. You set it to DC voltage to 20. The probes stay in the same ports. You want to put the red probe into the lead of the power connector and you put the black probe into the other lead of the power connector. If you get a negative voltage, Then switch the probes around, you will find the ground wire. OH by the way I did reconnect the TCU. I don't know if it still sends voltage with that TCU disconnected. I also heard a strange buzzing sound coming out from the hood of the car.

Anyways, I got 0.28 voltage on the Mainshaft Speed Sensor NM and I got 0.28 voltage on the Countershaft Speed Sensor (NC). And I got 3.72 voltage on the shift solenoid. So I'm assuming maybe the mainshaft speed sensor code 15 is good? And the power connector is good? Maybe it was the dirt build up on top of the sensor. That could be. That troubleshooting guide indicates if it has metal dusting on it, it wont work properly. Anyways I ordered another a mainshaft speed sensor just in case. I will wait to hook it up and see if the TCU code 15 goes away.

Any tips would be appreciated if anyone can help me through this TCU nightmare?


That little trick you are describing. Thank you. I take it that little trick is just a short cut of disconnecting the battery for 10 minutes to reset the ECU and TCU. Did you look at the techauto tripod transmission website? Maybe you could call up the Honda Dealership and see what their opinion is on the matter. For changing the TCU. I just leave all 4 nuts that hold it not tightened up. Or just leave two bolts on. Yes, it's not like changing a light bulb. I guess the problem is buying another TCU and finding out it doesn't work. And yes, the TCU computer reset trick only works for so long. And it eventually wont work it at all. I can't even remember the patterns of events that followed after the events occurred. My brain is kind of fried. And yes I usually don't close my hood either, I remember a mechanic stating that the hood would fly off because the hood is not locked in place. So I kind of figure why not just keep it up while I drive. LOL. Let's in theory think about this using that tech website. Let us say a damaged TCU may give false codes, or no codes. Perhaps you should be getting codes?

Let us say this. There are sensors on your car. 3 different speed sensors. The Shift Solenoid, the Lock Shift Solenoid. All parts and all sensors that are related to the transmission should be troubleshooted. And there maybe more as well. There is 15 of them. I had people tell me to take my car to mechanic. I think that would be pointless. Not only do you have to make sure your TCU is not malfunctioning. You have to make sure everything that works with TCU is working properly with it. I had emailed a guy asking him questions on possible damage to the TCU. He hasn't gotten back to me. It's possible you have to make sure there is no wiring issue going through your wiring harness as well. That's why it was very important for me to make sure these power connectors are working properly.

Have you taken a picture of your TCU uncovered?

Something is even happening even more weird in my case. My original TCU that has a damaged transistor is working better than the other TCUs. It's kind of really scary. Because I wonder if I rehook that original TCU up. It would no longer go more than 20mph. Because then I'm really screwed. The original TCU that is malfunctioning works better than the other TCUs. Perhaps that TCU is ignoring something with the sensors. That the other TCUs are not. I just can't remember what it was, I thought I remember someone telling me they actually unhooked one of their sensors to troubleshoot a problem.

 

Update: The guy that repaired my TCU. He never got back to me. He has ghosted me, or has missed the email, or I'm not sure why he hasn't replied? Perhaps I should give him a call and have him read the email. Or contact him on ebay.
Some mechanic in the local area has told me they don't even know how to test a sensor. I also contacted someone else at a part store. They claim they aren't even taught how to test out wiring issues, power connectors, or any such things. When they were taught how to repair cars at a local college.

Something is strange is going on here. I'm not getting much help here. To solve the mystery if these TCUs are damaged. And also how these sensors work. And also any possible wiring issues. I could use some help here.

I'm not sure replacing that sensor is going to fix the issue. The symptoms don't really fit. And it did pass its ohms test. Although it is still a slight possibility that it could fail in other ways. I know it's magnetic. And also depending on the temperature the ohms changes.