What does CPU use to display transmission gear on dashboard? - Drive Accord Honda Forums
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post #1 of 20 Old 03-17-2017, 08:49 AM Thread Starter
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What does CPU use to display transmission gear on dashboard?

Hi all,
Here is the conundrum. I have a 2006 Accord L4 with auto tranny. The car has 304k on it I love it.

Two days ago tranny started misbehaving. Just driving along at highway speed, steady speed, and suddenly the engine races to 4.5K and no power to the wheels. Taking the foot off accelerator many times "catches" and allows to continue to drive but then will "break" again into "neutral" mode.

While all of this is going on, the D indicator is not changing or blinking. Check Engine is not lit.
Downshifting to D3 or lower does not generally help, no more than taking the foot off accelerator. ATF level is normal. ATF is clean.

My theory is that one of the engine/tranny mounts is broken and as a result the shifting cable is not properly aligned with transmission case.
The force required to move the shifter has changed. It is harder now.
Also, 5 days ago I got bumped from behind while in traffic in D and full stop. Bumper was not damaged at all, and my car moved forward about a foot to 1.5 foot. I just waved the guy off at the time.
Now I am thinking maybe he "helped" me break one of the mounts causing this behavior.

So, the question to the collective wisdom is: What does CPU use to display gear selected? Is there a sensor at the shifter? Or does tranny signal what gear I selected?

TIA,

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post #2 of 20 Old 03-17-2017, 09:07 AM
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There is a transmission range switch right behind the black cover of the transmission in the driver's side wheel well. It's possible you have an issue with that.

But,... I have to ask, what was the last time you changed the transmission fluid. The symptom you described of losing a gear on the highway sounds like a fluid/clutch pack problem.

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post #3 of 20 Old 03-17-2017, 09:18 AM Thread Starter
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Quote:
Originally Posted by t-rd View Post
There is a transmission range switch right behind the black cover of the transmission in the driver's side wheel well. It's possible you have an issue with that.

But,... I have to ask, what was the last time you changed the transmission fluid. The symptom you described of losing a gear on the highway sounds like a fluid/clutch pack problem.
I changed ATF 10k miles ago. It's not ATF.

Are you saying that the range switch mounted on transmission is what CPU uses to light up a letter on the dash? Is this switch internal to tranny or external? Can it be replaced without opening tranny up?

Thanks.
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post #4 of 20 Old 03-17-2017, 09:39 AM
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In before @chris918 asks what kind of ATF you are running. He will think it is because of your ATF because the i4 AT never fails and its only the V6 AT that fails.

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post #5 of 20 Old 03-17-2017, 09:52 AM
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A suspected i4 tranny problem. Not even confirmed, and Probably something to do with the bump in traffic.

I4 tranny failures: 1
V6 tranny failures: can read about them all day on this site

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post #6 of 20 Old 03-17-2017, 10:06 AM
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If you think there is a problem between the PCM and the gear position indicator, then follow the attached troubleshooting step.

I still don't think that's the issue. The transmission is not going into neutral mode. I actually think the clutch packs are toast and gears are falling out of engagement. The car may think you are still in Drive, but mechanically, the gears fall out of engagement.
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post #7 of 20 Old 03-17-2017, 01:08 PM
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Same symptom happened to me once @ 450K. Changed the pressure switches, cleared out the old shift points, never happened again (so far - 32K ago). Did you purchase the car used, what fluid did you use for the change, how many drain / fills did you do & did you change the inline filter ? Like said above maybe worn clutch packs slipping trans. or a worn torque converter, both from neglected maintenance since new.

2004 4cyl. EX Sedan automatic, 487K.
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post #8 of 20 Old 03-17-2017, 05:35 PM Thread Starter
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Thanks for all the replies.
Yes, I am the original owner of the car. I have been using Castrol ATF for Japanese cars (made in Germany). My tranny has an interesting history.
Since about 50k it was making a bit of a wining noise. I ignored it. At 100k I changed ATF.
At 130k it started leaking from the axle seals. I had my mechanic change seals. It still leaked. He checked the seals and told me it was differential.

I went to transmission shop. He rebuilt the tranny. Differential was indeed very worn and needed replacement of gears.
Then at 168k I had a problem where when hot it could essentially "go neutral" but I also got blinking D and these codes P1733 P0780 P0796.
The transmission guy reopened tranny but could not find anything at all.
Long story short, it was an engine wiring harness which I replaced with my own hands and that solved the P1733 problem.

Unfortunately, the tranny guy did not assemble the axle seals correctly (I know that now, did not know it then), and since then my tranny leaked ATF slowly.
Towards 270k I was filling 1Q every 2k miles.
At 299K I brought it to my mechanic asking him to check seals and axle play. He told me the seals were incorrectly installed, replaced seals and replaced ATF.
It stopped leaking!
Now at 304k I have this.

From what I now understand, if it were engine/tranny mounts, since the tranny range switch is on the tranny itself, it is not likely that I would get a solid D while tranny actually shifts to N due to mis-adjustment of the shifting cable. Thank you guys for helping me figure this out.

As you probably noticed, I had not changed ATF between 170k and 299k because I was pouring new quarts in every so often. I never changed the inline filter (where is it located)? I strongly suspect the transmission shop did at 130k miles.

@KW2004Accord: did you have any trouble codes when you had similar symptoms? I don't have any codes at this time.

At this point I believe I am going to get tranny replaced with one from a junk yard from a donor car with 100000 on it. It was hit at 45deg on the rear bumper, causing left wheel to get fully out of it's place.
The replacement will cost me $170/picked up, with my mechanic charging in the range of $600 to do the swap. Hopefully will get done for slightly under $1k.

Words of wisdom on this plan are appreciated. I don't want to have this tranny rebuilt as this would be too expensive for my car.
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post #9 of 20 Old 03-17-2017, 05:51 PM
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Replacement sounds like a better choice than rebuilding a trans that has been rebuilt.

The filter, yes it does exist despite what dealers will tell you, is on top of the trans, kinda under the air box. Look for a black thing in the shape of a pop can but quite a bit smaller. Long needle-nose pliers (bent nose actually) will be needed to free the spring clips from the hoses.

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post #10 of 20 Old 03-17-2017, 06:00 PM Thread Starter
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Thanks for the info on the filter. How frequently do people change it? Does one pinch the tubes to prevent ATF leaks during the change?
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post #11 of 20 Old 03-17-2017, 07:15 PM
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post #12 of 20 Old 03-17-2017, 07:27 PM
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In before @chris918 asks what kind of ATF you are running. He will think it is because of your ATF because the i4 AT never fails and its only the V6 AT that fails.
Nope, in his own words, "these tranny's are fragile".

Can you even imagine how someone could think that a cubic foot block of metal gears and clutches that move a one ton vehicle is fragile?
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post #13 of 20 Old 03-17-2017, 10:40 PM
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Officially, there's no change interval. Dealers will tell you one of two things: it either doesn't exist (the non-existant part's part number is 25430-PLR-003), or never needs to be changed. Heck, it's a filter so it does get plugged over time and goes in to bypass mode.

Yearly? Every 30k? Every other ATF change is when I do it, or about every 60k.

It is directional so it does matter which way it's installed. No need to pinch the lines, it's not under pressure and only a little leaks out.

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post #14 of 20 Old 03-17-2017, 11:19 PM
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When my trans. slipped didn't throw any codes or blinking lights. Thank you for filling all the information in for us about your transmission history. I agree with the above posters, best if you can get another transmission put in. When you put in new trans. fluid the detergents start cleaning , that is what can cause the inline filter to clogg if you have a dirty trans. I change my trans. filter every 60K, others go much longer. Dealer wanted $40 for the filter - Amazon $25.50.

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post #15 of 20 Old 03-18-2017, 02:09 PM
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If you're gonna pull the tranny out, install an aftermarket oil cooler while you're at it. And I agree, a used tranny is the way to go. Good luck!


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