P1778 Stepper Problem

[abrusnahan]

Hey,

I have a 2012 Nissan Quest that threw a P1778 code. It was slow to start and a little jumpy upon acceleration. I went ahead and ordered the part on eBay and attempted to do the job myself. I dropped the pan and I think our setups our similar with the exception that my stepper is completely visible right when you drop the pan. It's sitting next to the filter. Well I took the filter off and the two screws holding in the stepper, and I let the ratio control arm spring back to it's starting position. Was that a mistake?

I installed the replacement stepper and hooked the actuator arm from the ratio control valve back into the stepper arm. I reinstalled the filter and the pan and replaced the lost fluid (with new fluid). Upon starting the vehicle, I cycled the gears to distribute the fluid evenly and everything was cycling fine, but when I removed my foot from the brake to actually engage the reverse, the van didn't move. I tried to engage the Drive and Low gear and got the same result—no movement.

I figured that the ratio control arm became unhooked from the stepper so I dropped the pan again and checked everything out. Everything seemed correctly installed so I reinstalled everything. Still got nothing when I put it into gear. I dropped the pan a 3rd time, this time deciding that I would just put the old stepper on since this one seemed to be a dud. I at least was able to move with the old stepper. However, when I got everything reinstalled, I got the same response—no movement.

Clearly, I've done something wrong, but I cannot figure out what it is. I checked the codes again and it's still showing a P1778 code. My gut feeling says it has something to do with the ratio control arm and the fact that I let it spring back to it's starting position but a guy on another forum said that shouldn't be a problem.

Can anyone help me with this? Any help would be tremendously appreciated as this is our family vehicle.

[macgiver]

from now on , start taking many sequential photos from START to FINNISH of any and all procedures .

[VStar650CL]

Anybody here actually changed a stepper? We don't do them at the dealership, we sell them a transmission, and the FSM is worthless, it says replace the transmission. So if anybody knows the nuances of changing one or has Aussie documentation with a how-to for the job, please chime in. I've helped this gent as far as I can, so someone who's actually done one or has an FSM with the procedure would be helpful.

[abrusnahan]

I do take pictures. That's why I'm at a loss. The problem is that I'm not a mechanic so if the problem is something miniscule, I probably overlooked it. I just pulled the entire valve body off and I wanted to see if anybody had any ideas about the upper end of the actuator arm that hooks into the stepper motor. It pushes into it's housing as if it's spring loaded but I'm curious as to whether or not it needs to be held at a certain position?

I'm going to try and embed a photo but if that doesn't work, then here is the upload URL (https://flic.kr/p/2oYmDsj)

IMG-0837 by Liam Tompkins, on Flickr

[macgiver]

I see , and you hope nothing ' dropped ' as that looks to me to be extruded out a little ? ya ? hmm See in the valve body exploded views what the hell is made up on, in, and around that valve shaft ?? good luck, Vstar the Genius here tho

[abrusnahan]

Do you have an exploded view of the valve body? Or could you tell me what you meant in your last post?

[VStar650CL]

Do you have an exploded view of the valve body?

Unfortunately, for the first 14 years of the CVT in USDM Nissan products, Nissan treated it like a black mystery box. We weren't even allowed to replace pulley assemblies. No parts were offered and no detailed documentation of the guts were provided. That's still pretty much true of the VB's. If anything is available in the way of exploded drawings and other details for an '09B VB, the only place you might find it is from Australia, where for some reason Nissan sold parts and let CVT's be rebuilt from the get go.

[abrusnahan]

Do you understand what Macgiver was trying to say in his last message? I know there is some sarcasm there but it seems as though he was trying to say something is supposed to be on, in, and around the valve shaft.

[VStar650CL]

No, but Mac is -- different. We love him, but you're not the only one who finds him sometimes incomprehensible.

[macgiver]

I was busy today , thanks guys for ironing out - I would never have thought it to be 'black box ' as Vstar educates us , sorry for assuming such , so sorry

carry on !

[abrusnahan]

I posted the same picture on NissanClub.com and I had a guy respond saying this:

Yes, at the position it was in before you detached it. The problem is you lost that point in space and the sensing sleeve could now be in deep space compared to where it was at first. That can lead to radical sudden pulley movement that can wreck the chainbelt to come apart as it has to move gradually (although that itself can be relatively fast) to stay in line with the pulleys, as soon as it is not then pulley misalignment can pull sideways on chainbelt to delaminate it and then it is scrap.

The chainbelt is always dead straight from pulley to pulley, if that gets off then too much sideways pull tends to make it come apart. What the outer end of that rocker to stepper is setting, The sensing sleeve is on same shaft as the moveable pulley axis and as the pulley opens up or closes back shut the sleeve registers the approximate amount of perceived ratio as determined by how far open the pulley is.

So does that mean there is a sleeve-like sensor on the little bar that the upper end of the actuator arm hooks onto? I'm assuming it can slide?