Manual Shift Mode

[wollip]

A reminder to check your manual shift control button occasionally - even if you are a flatlander.

 

The button on the end of the shift lever which drops the transmission out of overdrive and activates the manual shift mode failed incrementally on my 2012 2500.

The service tech (Gene)at North Point Nissan in Little Rock, AR diagnosed the problem with a combination of wizard like skills and a fancy voltmeter. As he said - high impedance in the switch contacts. Bottom line - shift lever assembly was replaced.

Gene explained that the button works in a fashion very similar to the buttons on an older cell phone or a tv remote - and that over time they can fail or not, depending on - luck?

[wollip]

Woe is me - I have the Sword of Damocles hanging over my head.

The problem with manual shift mode returned. As I drive it now to test it, it is failing to respond somewhere near 5% of the time. I don't want one of those times to be when I'm descending a steep grade with no shoulder.

I've had to wait a week for the tech guru to return from vacation but will be waiting for him early Monday morning.

If anyone has EVER had the button fail to respond and not allow you to drop out of overdrive and access your lower gears, I would appreciate hearing about it. Thanks!

[ASD Dad]

Mine acted up on one camping trip over the summer.  It would not get into Manual mode no matter what I did.  Once I stopped and restarted the van at a gas stop it was fine.  I only use it when camping and on hills but I tried it out last week after your first post and it was fine.  I will definitely be keeping an eye on it though.

[wollip]

ASD Dad-

Things for the input. Kind of scary when it happens - suddenly no control over a driving situation and more often than not no chance to reset it (stop and restart) until much later .

 

To update, I drove it home after seven hours at the dealership today. The local tech still thinks the problem is electrical (the signal from the button on the manual shift assembly not making it to the meter) while the Nissan tech team is leaning toward the possibility that the transmission is overheating and refusing the command.

The tech team is reaching out to Nissan Japan who will contact the Hitachi team that wrote the program that controls the transmission.

Sounds like it will be several days before an answer comes back.

In the meantime, we wait ....

[ASD Dad]

Overheating transmission?! Even towing big hills with the AC maxed my temp gauge never reaches halfway, we have a big cooler sitting right out in the airstream!

 

I'll start using mine on my daily drives and see what happens.

[KMG]

Just a thought.  Does the computer keep the transmission from down shifting if doing so will cause the engine to over rev?  When I was driving down the Going to the Sun road, once the manual downshift didn't work for me.  I thought it was a safety feature.

Edited October 27, 2015 by KMG

[wollip]

KMG-

I'm thinking this whole thing is more of a safety CONCERN. Maybe, as others report in with their experiences, we will be able to spot a pattern.

 

ASD Dad -

You have a transmission temp gauge?

[KMG]

If I press my vehicle information display button 3 times my transmission fluid temp is displayed.

[radin2son]

None of the displays have ever shown much if any movement once warmed up, no matter what the conditions.

 

When overdrive is pointless, I will use the manual mode. Downshfting from 4th to 3rd on a downhill can be felt and heard if the speed is too high, so I tend to brake, probably more than necessary, to the point where I think the shift will be smoother. On the Moki Dugway, it was slow going in 2nd, and I didn't put it into 1st until I had braked for each switchback or very rough section. It has never not shifted.

 

Climbing or slogging along in manual works like a charm. Whether you use the tach or your ears it is more intuitive...

[wollip]

So far, I've never had a problem with the shift paddle. And the button has never failed to return to overdrive.

It is the occasional failure of the button to activate manual shift mode that is my concern. Seems random and sporadic - without a pattern. But with enough input and occurrences maybe something will emerge.

Dope slap me for not knowing my vehicle - I did not realize that transmission display was there - or more precisely, didn't know what it was for.

I agree with Rad - never noticed any significant movement on those read outs - but I'll now be hawk eyeing the one for the transmission.

I'm guessing the local tech doesn't know that readout is there either because he made the comment that we could prove or disprove the tech teams theory by installing a transmission temp gauge.

As soon as it stops raining, I'll check the condition of the transmission fluid. If it has been overheating, it should be dark.

Many thanks to everyone for the comments and suggestions - keep them coming - we'll figure this out eventually.

[ASD Dad]

Did my drive this morning in manual mode for the fun of it.  Worked fine switching in and out of manual and actually using the paddle.  I'd use it to downshift coming to a stop or slow corners.

 

Yes, we have a gauge!  My Bully Dog tuner will also show the actual temp of the transmission.

[radin2son]

ASD Dad, Did you notice anything when you downshifted at higher speeds?

 

Thought about this last night; I use the manual mode most often when there are speed zone warning signs on secondary roads entering towns. If it looks like more than one stop sign/light town, or we are looking for fuel, just gawking, etc., I will engage manual mode. (Same for traffic jams.) The feel/sound in the shift from 4th to 3rd is most likely to occur going from 45 to a 35 mph zone. I'm not shifting at 45; rather, I shift after braking to 35 mph or so. The revs don't change audibly. Don't notice anything when going from 3rd to lower speeds.

 

Again, I've never had the manual button not work. No sounds etc., but the tach shows slightly higher rpm.

 

KMG, Have you tried putting it in tow mode. It acts like a speed limiter.

 

Here is another electronic related issue, or not, possibly related to the electronic brake force distribution (EBD). From day one, I have heard a faint sound when braking. It isn't mechanical, but sounds like pushing down on something spring loaded. When we were getting an "after the fact" NV orientation, I mentioned it. The cm at Dublin Nissan said he hadn't noticed this, nor had any one brought it up. It is faint enough that road noise drowns it out. I can still hear it, but it has never affected braking. Just ask the herd of deer near Eureka, NV I thought I was going to hit...

[KMG]

Whom ever goes and "Dope Slaps" Wollip, stop by my place and let me have it!  I just drove 6,460 miles forgetting I had the tow mode.  I guess because I wasn't towing I didn't think to use it.  Idiot!  Thanks radin2son.

Edited October 27, 2015 by KMG

[radin2son]

I am an "expert" in tow mode application, not because we tow anything or remember it on downhills; I inevitably hit the tow mode button instead of the inverter button to charge our phone. That is, when I remember to charge the phone or push the correct button and drive for miles thinking it is charging. My wife typically asks me, "Do you know you are in tow mode?" or Did you mean to push tow mode?" Actually, it is easier for the passenger to see both.

 

Curious, what is the 4x4 set up for engaging it and driving? Can this interfere with the manual mode?

 

Anyone wishing they had a clutch?

 

Just had this thought. Although the manual mode works shifting up and down, maybe it only was intended to engage when stopped and put it in the desired gear to prevent gear hunting in stop and go city driving, low speed zones etc. For those who have not had the button work while in motion, does it not work if you are stationary?

 

Also, does vehicle mass affect downshifting? If the system is car based rather than designed for NVs it could be too light duty. Then again, it could be a program issue.

Edited October 27, 2015 by radin2son

[KMG]

I'm not sure but I don't think my 4x4 and the shifting are interconnected.  While stopped, I engage my transfer case by lifting a lever in front of my seat next to the transmission tunnel.  A LED indicator on my dash next to our traction control switch illuminates.

[radin2son]

Wow! Purely functional.

[KMG]

That kind of sums up my whole van.  Purely function.  Nothing fancy.

[VStar650CL]

I'm the "Gene" Wollip mentioned, pleased to meet y'all.  By way of introduction, I'm a Nissan/ASE certified electical specialist with an engineering background.  I'm writing because I was concerned to discover that ASDDad had the same issue, so maybe Wollip's problem is something all Nissan technicians will need an answer for.

 

Some of you may be familiar with the old Sherlock Holmes quote, "When you have eliminated the impossible, whatever remains, no matter how improbable, must be the truth."  Some electrical issues can only be diagnosed that way, by process of (sometimes painful or unlikely) elimination.  It's especially true when "smartware" is involved, because no service manual gives a technician access to the code, or even a flowchart of how a device "thinks".  In this case, despite the intervention of a Nissan field engineer, we still don't know if it's even possible for trans heating to cause Wollip's issue.  Only the firmware programmers in Japan know the answer, and they haven't told us.

 

To help better-understand the problem, there are actually two firmware programs involved, the TCM (transmission controller) and the Meter (dash cluster).  The way the NV is constructed, there is no direct link between the Manual Shift button and the TCM.  The Meter monitors the button, then sends a CANbus message to the TCM when the button is detected.  So, in Newtonian terms, what we have is a multiple-body problem.  We can only try solutions in order of likelihood until something works.

 

The good news is, our field engineer is an excellent guy who's very good at his job.  He immediately saw what I saw in the wiring -- that the 12 volt signal from the button needs to be translated to a lower voltage for the Meter's microcontroller, and that's usually done with a CMOS "buffer" chip.  Certain manufacturing flaws can cause the inputs on those chips to "latch" under certain conditions, meaning they will no longer "see" the voltage applied to them.  That is, until the power is cycled, allowing the latch to clear.  This seems to both of us the most likely scenario by far, and it completely fits the symptoms of needing to cycle the key.  So we've ordered Wollip a Meter.  He'll need to tell all of us whether it worked.  If we happen to hear from Japan in the meantime, I'll keep y'all posted.

[wollip]

Gene-

 

Thanks for jumping in here and giving everyone an update on this manual shift situation - talk about straight from the horses' mouth :-)

[VStar650CL]

Least I can do.  Sounds like the answer might matter to more folks than you and me.

[ASD Dad]

Thanks for the update.  When it happens on mine the key cycle does indeed work.  Not exactly ideal in the middle of towing a 32foot camper down a mountain but the cycle fixes things (for now).  I havent used it much lately, I did for a few days just for fun to see if anything happened and of course it didnt when I was looking for the problem to happen.  

 

I have 3 trips to FL planned in the coming several months to go camping.  Each one will be around 1000 miles around trip.  Once south it's pretty flat so I wont be using the manual mode much after I get out of my state but I do use it for this section of the trip.

[VStar650CL]

Put the new Meter in this morning with instructions for Wollip to bring us the truck without cycling the key if it happens again.  I think that's the only way to isolate the problem if it still exists; at least the Consult3+ will be able to identify which system is rejecting the button.  Hopefully the latch-up thesis is correct and it's a non-issue.

 

Sad to say, still no reply from Japan.

 

Lately the reman house hasn't been requesting Meter cores back, so in 30 days I may be able to dissect the old unit and give y'all an update on the exact circuit and what went wrong inside.

[radin2son]

Gene, Thanks for the info.

 

Our 2012 NV V8 has never had any problems using the overdrive lockout button on the shift lever. Except for slightly higher revs, it is unnoticeable going from 5th to 4th.

 

Does speed have anything to do with the button not working? Is there a mph point where it won't work. Also is this a V8 and/or V6 problem?

 

This is a very basic question, but what is the intended function of the manual mode? Axulsuv long ago said it should be used to prevent gear hunting and wasted fuel in certain situations. I get this. As such, it works great in city traffic or climbing hills. Descending works, but it seems you already have to be in the intended gear from the start.

 

Is it intended to downshift? Our experience has been, no. You have to brake almost to the point where, perhaps beyond the point, where the automatic mode would downshift.

[VStar650CL]

Well, the engineers on this side of the pond (NNA) came through for our DTS, but this is an answer that will take some explaining.  BTW, Wollip, I tried calling your cell a couple times this afternoon but mine was acting up and I couldn't keep/get reception.  I'll just let you read and you can call me tomorrow on the shop phone.

 

Here's the story to date:  The Meter didn't solve it, but Wollip drove the vehicle to me when it acted up, without shutting the truck off.  There weren't any diagnostic codes (DTC's) in it before, but this time it showed up with an obscure P1815 code that specifically applies to the Manual Mode switch.  Trouble is, the documentation is awfully fuzzy.  I wanted to paste a copy so you could all see it, but the website doesn't like any of my graphic formats.  Basically, it says the Transmission throws the code whenever it sees "an impossible (button) input pattern" for 2 or more seconds.

 

Okay, so what's an "impossible input pattern"?  That's where our DTS came through.  Same deal with the wiring diagram, but for those of you who might understand, it's a simple grounding-switch setup with pullup resistors in the Meter to provide 12V bias.  The hitch is, the Manual Button is double-throw with the paddle only grounding through the normally-closed contact.  This means the paddle can't ground when the M-switch is pressed, preventing the button and paddle from operating at the same time.  There's also a center throw on the paddle that is also always grounded, except when the button is pressed.  So the paddle center pin signal always goes high (12V) when the M-button pin low, and vice versa.  It's supposed to increase reliability.

 

There is, of course, firmware in the Meter that reads and decodes all four switch lines.  That's where it gets murky.  The NNA engineer called it a "user induced" condition, implying that the driver causes it, but that isn't wholly accurate.  The firmware interacting incorrectly with the driver is a more apt description.  Bear in mind that any good firmware runs "self-tests" and detects errors, and in a keypad system, that includes stuck keys.  This will all come together when I describe the two conditions that cause the P1815:

 

1) The M-button is held for 2 seconds or more.  In this case the Meter decides the button is mechanically stuck, tells the Transmission to generate a P1815 and stops looking at the button.  It won't signal you that it has a problem, just continue to ignore the button until the key is cycled and the button (which has since been released) passes boot-up self-test.  The fix is to make sure you only, ever, press the button momentarily.  Never hold it, your Manual Mode will quit.

 

2) The M-button and paddle lines go high at the same time for 2 seconds or more.  This can happen if you're resting your hand on the shifter and the button is accidentally pressured by the palm or heel of your hand.  The "normally closed" switch throw breaks but the corresponding "make" puck isn't making contact.  Same result, the Meter ignores the button and the Trans throws a code until the key is cycled.  The fix is, rest your hand someplace else or in some other orientation.  Otherwise, your M-mode may occasionally quit.

 

This is only an issue because the firmware guys made the "stuck-button timeout" so short.  Having written quite a lot of realtime firmware, I can vouch that most keypad-driven devices have longer timers on input errors; tens of seconds or even minutes.  But, the NV's Meter is what it is.  There's no way to reprogram those sorts of operating parameters.  Perhaps a note in the Owner's Manual and/or Service Manual would have been nice, I'll try to noodge Nissan in that direction.

 

The silver lining is, now everybody will know what causes this and how to avoid it.

[ASD Dad]

Interesting. I don't drive with my hand on the shifter and I just pushed the button like always when mine locked me out. I may have pushed it several times in rapid succession when it refused to enter Manual mode but I didn't just hold it down.

 

My plan tomorrow is to make it ignore me by holding it down. I want to see what happens. I'll certainty watch for it the next time I'm towing.