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D4 light solid

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    #1

    D4 light solid

    I have a 92 accord wagon lx auto.

    I was driving 55mph when the car starting jumping back and forth between 3rd and 4th. The car did this for a few minutes after I stopped to check for any fluid leak (no leak).

    Now the cars current state is as stands.

    The D4 light is always on no matter what.
    When shifted into D4 , it's stuck in 4th gear
    When shifted into D3 , it's stuck in 4th gear
    When shifted into D2 , it's stuck in 2nd gear
    When shifted into D1 , it's stuck in 2nd gear

    Every time I come to a stop sign now I manually put it into D2 or 1 , get up to speed , then put it back into 3 or 4.

    Funny enough it actually feels like it drives better and smoother this way. lol But obviously something is broken and needs to be fixed.

    Some googleing says TCU and shift solenoids , but I'd figure I'd ask here as well. Keep in mind I'm an engine noob please. I really have no idea what I'm doing so I was going to change these parts randomly in hopes it fixed it.
    Tags: None
    #2
    It could be a number of things, but before you start replacing things that could be functioning properly, go pull the code. It's very easy and takes literally 2 minutes. Here's a thread on how to do it. Once you come back with the code, we can properly diagnose the problem.


    Also, check the stickies at the top of each section first. They are full of useful information, including the thread I linked you to.
    Originally posted by deevergote.
    And please, for the love of God, type like a human being!

    Comment

      #3
      The code can't be pulled , the D4 light is solid. Even when KOEO

      However through more googleing I'm 90% sure it's the tcm now. Apparently the problem has happend to other before and the capacitors die a lot.

      Comment

        #4
        A solid light is often an indication of a bad computer, yes.
        If you know anyone local with an automatic CB7, see if you can borrow theirs. It'll save you some money if the problem isn't the TCU.

        Keep in mind through your Googling... pretty much EVERYBODY says "my transmission won't shift. it's the tcu!"






        Comment

          #5
          I say if possible follow deev's recommendation, otherwise pull up the passenger carpet and pop open the cover for the tcu, and have a look at it, then visit the thread in my sig 'DIY TCU FIX'
          PT3/6 Development Thread | My 1991 LX Coupe | DIY: 90-93 Tcu Fix

          Comment

            #6
            I had this issue last summer, it was the TCU. I also had bad shift and lock-up solenoids and replaced them at the same time. The bad solenoids can do damage to the new TCU. They can be tested by unplugging them(front side of transmission) and testing the resistance with a multimeter.

            Comment

              #7
              The solenoids can damage the TCU if they're bad? That's news to me. Perhaps I should stop suggesting people try using someone else's known working TCU!






              Comment

                #8
                If you don't have anyone local that you can switch out your TCU with, there is another way to check if it is the TCU. You will need to take it out and open the TCU. Carefully look at all of the capacitors (one or more will most likely be leaking). Look for some goop underneath the capacitors. It took me several times and looking at it for a total of 2 hours, until I was able to notice the leaking capacitor on my TCU. There are companies that fix these, but you have to send it to them. Or you could try fixing it yourself.

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                  #9
                  Originally posted by emosun View Post
                  The code can't be pulled , the D4 light is solid. Even when KOEO

                  However through more googleing I'm 90% sure it's the tcm now. Apparently the problem has happend to other before and the capacitors die a lot.
                  Sorry about that. It was late and I was tired + stressed from exams. As others suggested, the TCU may be bad. They can usually be found pretty cheap though. Let us know what happens.
                  Originally posted by deevergote.
                  And please, for the love of God, type like a human being!

                  Comment

                    #10
                    Ok problem solved. I changed the tcu with another 92 accord lx wagon I found at the junkyard. Even though the cars are identical the tcu's are different part numbers.

                    Either the donor car had it's replace or my bad one was replaced. Either way , it's back to the way it was except it shifts earlier from first to second but I truly don't care I'm a slow driver and rather have it shift sooner then later.

                    Now to figure out why my torque converter is backwards , but that issue already existed and I'll make a different thread for it.

                    Comment

                      #11
                      Originally posted by deevergote View Post
                      The solenoids can damage the TCU if they're bad? That's news to me. Perhaps I should stop suggesting people try using someone else's known working TCU!
                      It is safe to swap TCU's for testing purposes but overtime the increased resistance of the solenoids would burn out transistors. Normally the resistance should be around 30-40 ohms i believe, my old solenoids ranged from 1,000 to 5,000 ohms. Good thing honda made the solenoids easy to get at. On the other hand a solenoid with too low a resistance could instantly fry a TCU, but ive never heard of such a failure occuring unless the solenoid was physicaly harmed.

                      Comment

                        #12
                        Originally posted by emosun View Post
                        Ok problem solved. I changed the tcu with another 92 accord lx wagon I found at the junkyard. Even though the cars are identical the tcu's are different part numbers.

                        Either the donor car had it's replace or my bad one was replaced. Either way , it's back to the way it was except it shifts earlier from first to second but I truly don't care I'm a slow driver and rather have it shift sooner then later.

                        Now to figure out why my torque converter is backwards , but that issue already existed and I'll make a different thread for it.
                        Different part numbers most likely just means that they have slightly different shift points, as you noticed. Shouldn't hurt anything.






                        Comment

                          #13
                          I had the same problem and went through 3 different tcu. Bought junkyard one at first worked for like 2 weeks then went to same problem accept this time it started flashing, but did the same transmission problems. I then ordered a new one of the internet and it worked for like 10 min. I sent it back and got another one same thing so i did some research and found out that it wasn't the tcu, it turned out to be the main relay. Replace that if the problem still exist then try tcu, but i can almost guarantee that it is the main relay.

                          Comment

                            #14
                            Originally posted by STOCKa6 View Post
                            It is safe to swap TCU's for testing purposes but overtime the increased resistance of the solenoids would burn out transistors. Normally the resistance should be around 30-40 ohms i believe, my old solenoids ranged from 1,000 to 5,000 ohms. Good thing honda made the solenoids easy to get at. On the other hand a solenoid with too low a resistance could instantly fry a TCU, but ive never heard of such a failure occuring unless the solenoid was physicaly harmed.
                            The automatic CB7s have an extremely notorious problem with TCU resistors burning out. This is the second place anybody should check (first thing you should check is the TCU code odviously). As one of the other more established members once posted, "The absolute, best, 100% fail-safe method of diagnosing a faulty TCU is by physically CHECKING THE BOARD within the TCU housing." I agree 101%

                            ALSO, here is a step-by-step on checking your lock-up and shift control valve solenoids.

                            The process is the same for solenoid lock-up control valves and shift control valves A and B. Pin A25 stays the same because it is the pin to ground. Here's a list of pins and wire color to check each solenoid individually.

                            Lock-up control solenoid valve A- use pin A6 (YEL)
                            Lock-up control solenoid valve B- use pin A4 (GRN/BLK)
                            Shift control solenoid valve A- use pin A5 (BLU/YEL)
                            Shift control solenoid valve B- use pin A3 (GRN/WHT)

                            First, disconnect the 26 pin connector for the control unit. Turn ignition switch ON and measure VOLTAGE between pins A# and A25 (BLK/RED). If there is voltage, you have a short to power in wire between the A# terminal and the control solenoid valve.

                            With the ignition switch OFF, measure RESISTANCE between the same two pins. Should be between 12-24 ohms. If NOT, check for an open in wire between A# terminal and control solenoid valve. If the resistance IS between 12-24 ohms, disconnect the 2 pin connector from the control solenoid valve assembly. Now there should be NO continuity between pins A# and A25, and you will most likely need to swap in a different control unit and recheck. If there IS continuity there is a short to ground in wire between A# terminal and control solenoid valve.


                            Hopefully this will save at least one person some time and money!
                            Last edited by 7cb7; 04-18-2013, 05:36 PM.

                            Comment

                              #15
                              Originally posted by greatwhitecb7 View Post
                              I had the same problem and went through 3 different tcu. Bought junkyard one at first worked for like 2 weeks then went to same problem accept this time it started flashing, but did the same transmission problems. I then ordered a new one of the internet and it worked for like 10 min. I sent it back and got another one same thing so i did some research and found out that it wasn't the tcu, it turned out to be the main relay. Replace that if the problem still exist then try tcu, but i can almost guarantee that it is the main relay.
                              The main relay controls the fuel pump. Nothing at all to do with the transmission. That's why the TCU didn't fix anything.
                              If the D4 light is on when it shouldn't be (or the S light on 90-91 models), it is a sign of a TCU error code (which I have said in this thread, and every thread on this topic... yet people still seem to ignore it...)

                              Originally posted by 7cb7 View Post
                              The automatic CB7s have an extremely notorious problem with TCU resistors burning out. This is the second place anybody should check (first thing you should check is the TCU code odviously). As one of the other more established members once posted, "The absolute, best, 100% fail-safe method of diagnosing a faulty TCU is by physically CHECKING THE BOARD within the TCU housing." I agree 101%
                              Finally, someone has sense! Thank you!

                              The TCUs do seem to fail often. One of the causes (one that I recently learned myself) is due to the solenoids failing and frying the TCU.






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