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hey bro I just got a p1777 yesterday and I'm freaking out because they told me the exact same thing for my car I have a 08 Altima too but noticed that the 2008 one wasn't on there are the other ones a good substitute
Yeah, I'm still without my JX35 Infiniti for the moment. I never got a part number for the stepper motor, but I did find the valve body for sale on eBay. To look at the photo of it, it almost appears that there is no stepper motor there. :confused: Maybe that's why I can't figure out the stepper part number. Anyway, I can have a new valve body assembly for around $400. That, plus the cost of jack stands plus the cost of a replacement oil/filter will still be WAY cheaper than any option Infiniti will give me. I figure there's not much to lose trying to fix it myself. I've watched enough YouTubers change theirs on various Nissans/Infinitis that I feel comfortable giving it a go. I'm no mechanic, but I'm not mechanically stupid either.

Luckily, I have two more vehicles to drive!

John
 

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I'm not sure if Benzolorenzo1 active anymore, but I'll take a stab at some of the comments, as I've been immersed in this for the past couple months.

The stepper motor is tied to a ratio control valve on top of the valve body. In my case, I got code P1778 and the car performed like it was stuck in a high gear. It can get stuck in any gear ratio. I replaced the valve body myself (which includes a new stepper motor) and got past that particular issue (although I had other issues). The ratio control valve was stuck on mine, so it didn't allow the stepper motor to move and do what it needed to do (change the ratio in order to "shift gears").

If your car is stuck in that one ratio and isn't just sometimes getting stuck, then my best guess at solutions are:

A) Take the valve body off and see if it is the motor or the ratio control valve next to it. The valve is spring loaded. If you are able to push the rod for that valve in and have it spring back, then my guess would be that it is the stepper motor and you could just buy that and replace it.

B) If it is the ratio control valve, then I suppose there is a chance you could disassemble it and see if you could get it to move freely. I couldn't find the parts online to replace the parts for the ratio control valve, but if anyone knows of a source, I'd like to have that.

C) You can buy a whole different valve body, which includes the stepper motor and ratio control valve. The reason I did this is because I figured a car with 120K miles probably could benefit from a remanufactured valve body, where the solenoids and other valves had been cleaned and tested and replaced with other parts that were operating at spec.
How did you make out with your valve body replacement? I'm getting ready to do it as well. One question, did you have to get the TCM reprogrammed before driving after installing the new one?
 

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About 6 months ago I received the death code P1778 (stepper motor) in my 2008 Altima. I searched far and wide, low and high, only to be told 2 things... you need a new transmission, or you need a new valve body. since I didn't have $2500 for a new trans, let alone $800 for the valve body I decided to look into this a little further. watched a youtube video the only one I could find was a Nissan armada, but thought what the hell. I drained the fluid, dropped the pan, yanked out the valve body, and found that little bastard that gave me such trouble.

now with part in hand I went to my local parts store, and told we don't sell that part, its not even in our system... went to the dealership, told the same thing and was told I needed to buy a new transmission as they are not "serviceable" funny but I had the part in hand, how can it be not serviceable?

lastly I took a gamble, I went to ebay, ordered a stepper motor. 20k miles later, still no code, no whine, and no lock up. here is how I saved thousands and bought a $35 part.

1)drain fluid.
2)drop pan (clean with brake cleaner)
3)remove the 3 bolts holding filter. (clean with brake cleaner while your at it)
4)remove the valve body about 11 bolts
5)remove the stepper motor from the top of the valvebody (the side you can't see with the pan off) 2 bolts
6)replace with the new stepper motor found here JF011E RE0F10E F1CJA Transmission CVT Stepper Motor For SENTRAN Nissan Dodge | eBay
7)take a piece of dental floss about a foot long and hold the spring loaded arm back against the stepper motor and return the valve body back to the transmission.
8)after you have a few bolts in place remove the floss before you tighten all the way.
9)reconnect trans filter and bolt back into place.
10)rejoin the fluid pan to the transmission and replace with quality cvt fluid. Amsoil makes a great product.

I hope this helps and if you have questions please feel free to ask.
Outstanding my good man you did a great job! I just replace my valve body today, come to find out my stepper motor control arm wasn’t locked in place all the way. So, I’m gonna have to retrace my steps with a small allen wrench or a skinny screwdriver again… But, I didn’t think about the whole dental floss thang😲 👏🏾NICE!!💯
🤙🏾😎🤙🏾
 

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About 6 months ago I received the death code P1778 (stepper motor) in my 2008 Altima. I searched far and wide, low and high, only to be told 2 things... you need a new transmission, or you need a new valve body. since I didn't have $2500 for a new trans, let alone $800 for the valve body I decided to look into this a little further. watched a youtube video the only one I could find was a Nissan armada, but thought what the hell. I drained the fluid, dropped the pan, yanked out the valve body, and found that little bastard that gave me such trouble.

now with part in hand I went to my local parts store, and told we don't sell that part, its not even in our system... went to the dealership, told the same thing and was told I needed to buy a new transmission as they are not "serviceable" funny but I had the part in hand, how can it be not serviceable?

lastly I took a gamble, I went to ebay, ordered a stepper motor. 20k miles later, still no code, no whine, and no lock up. here is how I saved thousands and bought a $35 part.

1)drain fluid.
2)drop pan (clean with brake cleaner)
3)remove the 3 bolts holding filter. (clean with brake cleaner while your at it)
4)remove the valve body about 11 bolts
5)remove the stepper motor from the top of the valvebody (the side you can't see with the pan off) 2 bolts
6)replace with the new stepper motor found here JF011E RE0F10E F1CJA Transmission CVT Stepper Motor For SENTRAN Nissan Dodge | eBay
7)take a piece of dental floss about a foot long and hold the spring loaded arm back against the stepper motor and return the valve body back to the transmission.
8)after you have a few bolts in place remove the floss before you tighten all the way.
9)reconnect trans filter and bolt back into place.
10)rejoin the fluid pan to the transmission and replace with quality cvt fluid. Amsoil makes a great product.

I hope this helps and if you have questions please feel free to ask.
Lorenzo, dud this is why I joined to get knowledge from good people like you. Thank you for this great post brother!!
 
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