Hey everyone, first post here. Long time lurker.

So during this ridiculous cold snap here in Canada, the car sat for a few days, (plugged in). Unfortunately the frigid temps took a toll on the battery, and it needed a few hours on a charger before it would start.

Now, after it started, it idled for close to half an hour since ambient temperatures that day were closing in on -40. After I jumped in to head off to work, I noticed the intelligent key light was on in the dash. Note, this light has never been on before, so I chalked it up to the key fob battery being weak. It turns off once out out park.

Normally in these temps I'll do a few laps around town just to help warm things up, and shortly after hitting the highway I had a SES light pop up, and my rpms were around 4000 at approximately 100km/h. I put the shifter into manual shift, and the dash was displaying 4th gear. Bumping it up to 5th and 6th made no change to rpms.

So, excitedly I turned back for home to do a code read to find I had a P0744, and a P1778. Fantastic. Death codes. Too cold to do anything with it anyway.

So a few days later, I cleared to codes and set out around town again. This time it threw a P0840. But the car drove just fine at the lower speeds.

Once the temp warmed up to a toasty -30, I pulled the CVT dipstick, and the fluid is dirty looking. I've never swapped the fluid out myself. 180,000 kms.

Now, I've purchased the stepper motor for the valve body in the CVT along with some fresh fluid and I'll be swapping it out this weekend.

My questions are, has anyone had any similar experiences to what I have described? And what the hell is up with this Intelligent key light?

Thanks!

Intelligent key problem first. Probably a fluke due to the cold weather. Replace the fob battery. Also, out of curiosity, do you have a spare fob?

Has the CVT had the regular service as recommended by Nissan?

CVT TRANSMISSION FLUID
Over time, CVT fluid can lose the necessary properties and should be replaced periodically. It is also important to check the transmission for fluid leaks to repair if necessary.

Service Frequency
Inspect every 24,000 kms or 12 months. Replace the fluid every 96,000 kilometers or request the dealer to inspect the fluid deterioration data using a Consult. If the deterioration data is more than 210000, replace the CVT fluid.

Is this the original CVT, or was it replaced under the extended warranty? Nissan extended the Altima's powertrain warranty (2007 to 2010 models only) to cover CVT problems for up to 10 years or 120,000 miles.

Chupacama wrote: ↑

Wed Feb 17, 2021 11:39 pm

Once the temp warmed up to a toasty -30, I pulled the CVT dipstick, and the fluid is dirty looking. I've never swapped the fluid out myself. 180,000 kms.

Now, I've purchased the stepper motor for the valve body in the CVT along with some fresh fluid and I'll be swapping it out this weekend.

If it's never had a fluid swap, at that mileage there's a great likelihood that it has problems bigger than just a valve body. You should rent a borescope from the local parts store and have a look at the belt. If it's scored then return the VB and save your money, the tranny is toast and will need a rebuild. Take a look at this bulletin, it will give you a good idea of what to look for:

https://www.nissan-techinfo.com/asistgc ... /1UW15.PDF

Thanks for the replies. The intelligent key behaves the same with both fobs, both with new batteries. I noticed the light goes out once taken out of park. Also noticed there's no door chime, and it doesn't display when the vehicle is in park.

I pulled the codes from my last trip and I got P0744 &P0840. I checked the transmission fluid, and the level looks ok. Color is dark greenish and smells like transmission fluid.

Regardless, I'll pull the pan and swap out that stepper motor and give it some new fluid since I have it on hand. I've never changed the fluid myself, and I can't confirm if it's been done.

I don't have access to a bore scope, unfortunately. The old millwright in me is just giving me the feeling that it could be electrical, with the battery being discharged during the cold and the sudden issue with the key. As noted before, it drives absolutely fine up to 60km/h and then the CVT stops CVT'ing.



Thanks again for the input, and I welcome any more advice and I will update when I can. Cheers!

Chupacama wrote: ↑

Fri Feb 19, 2021 12:01 pm

Thanks for the replies. The intelligent key behaves the same with both fobs, both with new batteries. I noticed the light goes out once taken out of park. Also noticed there's no door chime, and it doesn't display when the vehicle is in park.

I pulled the codes from my last trip and I got P0744 &P0840. I checked the transmission fluid, and the level looks ok. Color is dark greenish and smells like transmission fluid.

Regardless, I'll pull the pan and swap out that stepper motor and give it some new fluid since I have it on hand. I've never changed the fluid myself, and I can't confirm if it's been done.

I don't have access to a bore scope, unfortunately. The old millwright in me is just giving me the feeling that it could be electrical, with the battery being discharged during the cold and the sudden issue with the key. As noted before, it drives absolutely fine up to 60km/h and then the CVT stops CVT'ing.



Thanks again for the input, and I welcome any more advice and I will update when I can. Cheers!

While that is a LOT (likely too much) of distance w/o fluid changes also keep in mind the CVT is VERY sensitive to fluid volume,
So be absolutely certain you add the right amount when you refill.

PalmerWMD wrote: ↑

Fri Feb 19, 2021 3:35 pm

While that is a LOT (likely too much) of distance w/o fluid changes also keep in mind the CVT is VERY sensitive to fluid volume. So be absolutely certain you add the right amount when you refill.

Good thinnin', Palmer. Yes, underfilling won't hurt anything unless the fluid overheats, but overfilling causes foaming which is very damaging very quickly. Always refill with less than whatever came out, warm it up fully, then top off. Err low and not high.

Quick update, dropped the fluid, changed out the stepper motor on the valve body. Got new fluid in and at the correct level.

Still having the same problems. Took it for a short drive, still revs out at 4k rpms at highway speeds. Returned home and pulled codes. Got a P0745, P0840 and P1778.

Chupacama wrote: ↑

Wed Feb 24, 2021 11:08 am

Still having the same problems. Took it for a short drive, still revs out at 4k rpms at highway speeds. Returned home and pulled codes. Got a P0745, P0840 and P1778.

Trashed belt, I was afraid of that. That's why I suggested the borescope.

Welp, is what it is. Shouldn't be surprised given the mileage. I appreciate the help from you all.

Now, where my car is an 08.... I'm seeing two different production dates for selecting a replacement transmission. Ones thru 06/08 and the other is from 07/08. How do I find out which date of manufacture my car is? Is it deciphered from the vin number, or is that info on the info sticker that's in the door jamb? Thanks

It's on the door jamb.

VStar650CL wrote: ↑

Fri Feb 26, 2021 8:13 pm

It's on the door jamb.

Thanks!

Just a thought, I was looking through my past parts orders and I noticed my item description for the stepper motor I bought states RE0F10A, which is from what I understand for the 2.5.

Physically it was identical from to the one I removed. So, am I correct in assuming I installed the wrong part?

I'm pretty sure everything in the RE0F10x series used the same stepper, and as far as electrical function, a Jatco stepper is a stepper is a stepper. So the RE0F09B for the 3.5 may use the same one. If the dealer ordered the parts according to your VIN, it should be the right one.