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Discussion Starter · #1 ·
My wife's 2012 Altima.... 2.5s just recently started having this issue after a 600 mile trip. We live in the mountains so it is a little hard revving climbing the mountains but other than that we had had no issue. Then this last trip suddenly midway in the trip up the mountains trough the canyon her car suddenly revved up past 3 RPM to almost 4 then started sputtering and lost acceleration down to 35 MPH. In city where there is no real hills it revs low and does basic driving it needs in town. Easily reaches 45, even 55 if needed. Up a hill or to get to highway speed though is a whole other story I can rev it up to 3RPMs or even 3.5 RPMs and takes forever to get to speed and if going uphill it looses acceleration fast to 35 and anything past 3.5 RPMs on this it starts to sputter and if i release the accelerator it levels off and runs fine. Seems to be no shifting at uphill or highway which I was able to hear when she first got the car a year ago. Any suggestions on what to check out or what this could be? I am also fairly sure she has the dreaded CVT transmission.
 

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From your description, it sounds like there's a problem with the CVT; it's probably going into "fail safe mode" due to possible overheating. However there are many other conditions in the CVT that could cause the CVT to drop into "fail safe mode"; the Transmission Control Module (TCM) sets this mode so that operation can be continued even if the signal circuit of the main electronically controlled input/output parts is damaged. One of the first things to do is perform an ECU/TCM code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the Factory Service Manual (FSM) for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM from this web site: Owner's Manuals. The section TM is the one you need to read.

If the CVT only goes into "fail safe mode" when fully warmed up, then the suspected failing component may possibly be the fluid temperature sensor circuitry; this is just a guess, so the code readout is essential. Codes P17F0 and P17F1 never turn on the MIL on any Nissan model. P17F0 is the CVT "death code", it means severe belt slippage was detected.

The symptoms you describe seem to indicate judder. Judder will be most pronounced on a moderate to steep incline with light acceleration. Let off the gas at mid-hill, let the car coast momentarily down to 20~30 mph, then apply enough pedal to roll back up to speed. It should transition smoothly. If you feel any shuddering or surging, or the tach starts jumping around without pedal input, that's judder.

To enhance longevity, the CVT fluid should always be replaced every 30,000 mi. When the fluid stays in too long, the chemical properties of the fluid get compromised and it can no longer provide that cushion that's so needed between the steel belt and the cones. The fluid has two great enemies, and temperature is only one of them. The other is shearing force generated by normal operation of the belt, which increases on hills or with a load. This gradually breaks down and shortens the long-chain molecules that cushion the belt. You can generally deduce that by looking at the fluid; if it's very dark brown and has a burnt odor, it's shot!
 

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The TCM firmware on a '12 won't have "judder detection", that came in with the gen5's in '15 and was retro-added to '13~'14's by a recall. So your '12 won't throw any P17Fx codes, the firmware isn't equipped for it. However, it definitely does sound like your belt is slipping.
 

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Discussion Starter · #4 ·
I know I changed the serpentine belt about 3 months ago cause the old one literally snapped in half in a month and the one before that shredded over about 9 months from buying it. My wife worked at the lot she got it from and it had recently been repo'd from a lady whose boyfriend decided to get the cheapest struts put on and supposedly did performance upgrades which I have slowly been correcting his mistakes. I know the car is at 190,000 miles it was at 170,000 when we got it but other than oil and filters and the corrections I have done to fix other issues that gals boyfriend made This has been the biggest issue. I will take it somewhere and may even call and see if it still has any kind of warranty on it to get it fixed. I will let you know what comes of it.
 

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I think we're talking about the belt/chain inside the CVT, not the exterior serpentine belt.

However since you mentioned the serpentine belt breaking in two weeks, either the belt was installed incorrectly or an old belt was installed; could also be the wrong size was installed.
 

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I think we're talking about the belt/chain inside the CVT, not the exterior serpentine belt.
To clarify for the OP, CVT transmissions have no "gear changes" like a normal Automatic Trans. Instead they use steel belts riding on two steel pulleys. The width of the pulley grooves can be changed hydraulically to make the effective diameter of each pulley smaller or larger, rather like the gears on the pedal and wheel of a 10-speed bicycle but using a belt instead of a chain. It obviously takes enormous hydraulic pressure to hold a belt like that in place without slipping, and any glazing or deformities in the belt or pulleys can prevent it from "grabbing" and moving the car. The symptoms your tranny is exhibiting generally mean a damaged belt that can no longer hold under power.
 

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Discussion Starter · #7 ·
ok so would the belt or belts be able to be changed or is it a full tranny replacement? I should have remembered this darn CVT tranny has a belt with the research I did for a friend with a 2010.
 

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ok so would the belt or belts be able to be changed or is it a full tranny replacement?
Nissan makes rebuild belt-and-pulley and Valve Body kits for most of the RE0F10 types, but it takes special measuring tools and specialized knowledge to do the repair. Unless you know a Nissan tech who will do it on the side cheap, you're probably better off with an already-rebuilt unit from NissanPartsDeal.com or a good used unit with the donor TCM included.
 

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And to add to that, whatever you decide to do, add an external trans cooler and drain and refill the CVT fluid once a year since you drive in harsher conditions...in my opinion. I would rather spend the extra money on the CVT fluid to know it will last longer.
 
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