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2005 G35x Manual Mode/M intermittent / works 20-30% of the time

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2005 G35x Manual Mode/M intermittent / works 20-30% of the time

Old 11-03-2018, 11:45 AM
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Angry 2005 G35x Manual Mode/M intermittent / works 20-30% of the time

Been through hell and back with this issue. I just want to finalize it as nothing else major is wrong my 05 G35x ... It's got high KM, 230+, but runs like a dream!Sometimes it will stay in M-mode the whole trip, but MOST of time its kicks back into D after about 5-10 seconds after starting the car and driving. Once it fails, it will not register M mode until you the next time you drive, potentially lol. Occasionally, you can turn off the car and restart it and it will fix it. Also, the downshift/upshift doesn't register sometimes and may take several taps to actually shift, but it's the downshift really 99% of the time... it also very rarely will shift own its own in M-Mode, down shifts only, without human input, which is very annoying, but this is rare. Outside tempature also seems to affect its oeprtion of working or not. I'm sure all the issues are related to one thing... I hope! Because it does work fine sometimes...

Work done already to address this issue:
- Replaced shifter assembly - as suggested by Infiniti ( Did not work ) Cost: $1000.00
- New valve body/TCM - as suggested by Infiniti , was covered under my used car warranty ( IT DID NOT WORK ! ) only had to pay $700 under warranty, would've been $2,800 otherwise..

Now Infiniti is saying it's my combination meter ( Guage Cluster ) , showing code: P1815 Manual Mode Switch - I'm RELUCTANT to listen to them anymore... Quote on the Combination is $2000, but Iíve been looking into used ones or refurbishing my current one for much, much cheap than that. My warranty might cover it, but I hate to waste it on issues like this! It does make sense that this could be the issue though, but why wouldn't they diagnose this in the first place?? Dealerships are total rip off! but most places say they are your best bet for this issue...

Some other research I've done, people say it could be a cam sensor, but I don't see how that could cause all these issues...Could it be a speed/wheel sensor? Tranny fluid?

It does have a minor electrical issues in the combination meter - left turn signal on dash is faint inside most of the time, and sometimes work normal, and the gas gauge gives a faulty reading. I don't think this is this all connected to the M-mode issue and the combination meter? Am I going to just keep wasting money, or, have I eliminated all possible causes and the combination meter ( Gauge Cluster ) is the fix?? I need this fixed now!! LOL!

Please help!!!
Old 11-09-2018, 11:42 PM
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Clean your grounds? Check wiring harness for issues?
Install grounding kit?
Just throwing some possibilities out there. Could just be a loose wire or a bad connection somewhere. GL
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Bonesg35x (12-21-2018)
Old 12-21-2018, 07:00 PM
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Thanks man!! I appreciate it. Yes, others have suggested this and i'm looking into it.

I'll update if this helps!

Old 12-21-2018, 08:03 PM
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My 06 acts like that and I get the 1815 code every now and then. I know there are some magnets in there and two switches I think that might need to be cleaned, but since you said they replaced the shifter already not sure if it applies. It's possible your combo meter is messed up. The fuel gauge could be related to the senders on the two fuel level senders in the tank though. You can also do a self test on the combo meter too, but not sure if it tests anything with the manual mode switch. I had this problem on my Audi as well and at first it was the magnets, but it eventually required a new shifter and PNP switch. The PNP swith in the Audi though is a lot different than the G, so I don't think it applies here.

The combo meter when it manual mode reads that it's in that mode and then sends the commands to the TCM.
When in auto mode it reads it's not in manual mode and sends that to the TCM instead.

It sends the up signal from the shift on pin 8 to the combo meter, down on pin 7 to the combo, pin 6 is a neutral, pin 10 is used when it's in auto mode, and 9 looks like a ground wire.

They sure made a hell of a lot money throwing the parts cannon at it!

Looks like pins 4/5 go from the combo meter down to the TCM. Pins 1 and 24/25 on the combo meter look like they goto a shared ground wire between the combo meter and the A/T shifter assembly (pin 9).

I'm not a pro, so I could be wrong in things I'm reading, lol. I'm just looking at AllDataDIY and going off my knowledge and experience I have from working on my G and other cars.

They sure made a h3ll of a lot money throwing the parts cannon at it!

Last edited by coffeysm; 12-21-2018 at 08:09 PM.
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