Infiniti G35 Automatic Transmissions

msidman

Hey everyone, I've been having an issue lately with the automatic shifting of my 04 G35 Coupe and I can't seem to figure out what the problem is. I've taken it in to the dealership multiple times and the mechanics are never able to reproduce the problem... it happens sporadically, but enough so that it's making me worried.

Basically what is happening is that around 40 mph or so, or slightly thereafter, my car upshifts, but the upshift is extremely hard and not fluid at all. The car almost jolts itself, and I can feel vibrations in the peddle from the engine. This usually only occurs when I am accelerating slowly. Fast acceleration there is no problem. There also isn't an issue when I'm in the tiptronic mode, so my guess it has something to do with the programming of the automatic transmission.

I think when it shifts it is switching up to 4th gear... it's never occured when downshifting, only accelerating slightly in automatic. I recently had a 30,000 mile service completed, and they replaced the transmission fluid, so it's definitely not that. Otherwise I stay up to date on all oil changes and other service appointments.

Does anyone know what might be the cause of this problem? Any help is appreciated. Thanks!

scottm123

I've heard that there is a way to reset the adaptive learning mode in these trannies.
I wonder if resetting this would cause the system to relearn and maybe resolve this little quirk? :confuse:

It sounds like a programming issue more than a mechanical problem, since the manual mode shows no signs of a problem.
Flashing the tranny's memory may correct the problem.

msidman

I agree with you on the fact that I think it is a programming issue, otherwise I would have felt it in the manual mode...

I did some background research and found this on Consumer Guide Auto:

"Automatic transmission: The automatic transmission may engage slowly, shift hard or into the wrong gear requiring reprogramming of the transmission control module. (2003) "

The only problem is that the dealership refuses to do anythign unless it can reproduce the problem... which it has not been able to the past 3 times I have taken it in. Is there a way to reset the transmission or flash the memory manually? Or do I have to convince these guys something is up..?

scottm123

I know this can be done yourself, but every car is slightly different and I honestly don't know off the top of my head.
Hit the guys @ G35Driver and ask there.
I don't have access to there while at work.

msidman

Nice, thanks for your help. I actually went over to their forums and found a whole section on reprogramming the ECU.

I found an even better link right here which walks you through the steps: ECU Resetting Procedures

I haven't tested it out yet but hopefully this fixed this issue.

msidman

Well, I tried resetting the ECU... but of course it didn't fix the problem. I was leaving the country at the time so I sorta hoped that after 3 months it would fix itself, which it didn't either. So now I have no idea what the problem could be. I've taken it to the dealership multiple times about this problem and of course they can't reproduce the problem. Any help would be appreciated. Thanks guys.

jray2049

I'm having the same symptoms you describe. I'm going in for 60K service on Thursday, so I will ask them if they have heard of this before. I also will have trouble demonstrating it for them. It's been happening for at least a couple years, but it seems to be happening more frequently now, but perhaps that is due to less pedal to the metal due to high fuel prices. (Like you say, it only happens with light acceleration, not heavy.)

Did you ever find a solution?

Thanks.

msidman

I could never convince the dealers that there was a problem so I stopped trying... I actually go to school in Miami, and didn't notice a problem down there, but I think it's because there was a lot of stop/starting in the traffic, and I wasn't able to really have the distance to accelerate slowly.

Now that I'm back on the Cape I've noticed it a lot more, especially because I am trying to conserve fuel by not accelerating hard.

Let me know if you find out anything from your dealer.

jray2049

Sure found out a lot from the dealer:
"Never heard of that."
"No error codes are shown." (I asked if any error codes were logged.)
"No updates are available." (I asked if there were any tranny firmware updates.)
"Unable to confirm." (As we expected.)
Oh well. If it doesn't get worse I can live with it. If it does get worse, I have two years left on my extended warranty...

esfoad

I hope this helps you. I got this from the G35 Driver so kudos to them:

ECU Resetting Procedures

Timing is extremely critical. If it is NOT DONE within the specify time, the ECU will not reset and the Check Engine Light (CEL) will continue to remain ON.
A stop watch or an analog clock with a second’s needle will be useful.

Operations Procedures for Basic reset.
1. Confirm that accelerator pedal is fully released, turn ignition switch “ON” and wait 3 seconds.
2. Repeat the following steps (2a and 2b) procedures quickly five times within 5 seconds.
2a. Fully depress the accelerator pedal (HARD).
2b. Fully release the accelerator pedal.
3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 10 seconds until the CEL starts blinking.
4. Fully release the accelerator pedal (while the CEL is still blinking)
5. Wait about 10 second.
6. Fully depress the accelerator pedal and keep it for more than 10 seconds.
7. Fully release the accelerator pedal (The CEL light will continue to blink).
8. Turn ignition switch to “OFF” position and now you can start the car. The CEL light should be gone.

If the CEL light continues to remain ON, repeat the above steps. Timing is EXTREMELY critical to resetting the ECU.

Hope this works. There are also directions on Accelerator Pedal Release Position Learning, Throttle Valve Closed Position Learning and Idle Air Volume Learning (Throttle Position Learning). So if you want those either I will post here or just go to G35Driver and do a quick search.

msidman

I actually have a print out of those exact directions for the ECU reset and others, but thanks for the post! I thought for sure it would fix the problem, but I've done the ECU reset probably around 10 or so times, and it doesn't seem to get any better.

Just my luck... of course. I've sort of given up on the problem and have just dealt with it.

Over time I've actually been able to predict when the shifting problem is about to occur... it almost seems as if the engine gets stuck at lower RPMs when it hits around 40 mph. (For example, I will be pushing on the accelerator and the RPMs won't increase as they normally do, albeit they might do it slightly slower).

If I know its coming, most of the time I can break it by accelerating harder, and then taking my foot off the gas, sort of powering it through to the next gear.

adbrick

Just purchased a 2004 G35X with 56,000 miles. The rpms at 70 MPH are nearning 3500. Is this normal. At 55 mph they are 2200. Seems high for a 5 speed auto. I notice when I am in autoshift that it only goes to 4th gear. I was told this was a 5 speed auto with overdrive.

soukie123

transmission seems like it can't get to overdrive when driving 45-55 mph..dealer says the trans learns my new speed habits and adjusts to that..how does it learn the old way..thanks