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Discussion Starter · #1 ·
Hey everyone,
My girlfriend has a 2010 Murano that's giving the P1778 stepper motor code, and not "shifting" (yes, I know CVTs don't shift gears, but you know what I mean). I ordered a stepper motor off of amazon, drained the transmission, replaced the motor, filter, and pan gasket, and filled the trans with the correct NS-2 compatible fluid. I cleared all codes with my scanner, although I know that "permanent codes" like P1778 have to clear on their own after X drive cycles and Y miles.
I started the car, no check engine light. warmed it up, checked the fluid level and made sure it was good, then drove it around the block. It "shifted" as it should, doing 65mph while turning approximately 1500 RPM. I got a little stutter from time to time, but I assumed the computer was learning the new stepper. Checked the fluid again when I got home, level good. This was Thursday. She drove it to work Friday, and an hour and a half round trip to drop her son off with his dad on Friday. It sat the rest of the weekend, as we took my truck.
This morning, she tells me that the light has came back on, and it's starting to exhibit the same behavior. She stuck the scanner back on it at lunch today, and the P1778 code is still there. The scanner claimed there were two other codes, but she said scrolling down just showed more of the same. Any idea what I could be looking at here? I'm pretty mechanically capable, but my experience with CVTs is zero aside from what I've learned about this one already.

Any help is appreciated!
-
 

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First a question: how many miles on it?

We experienced something similar: last summer I replaced the stepper motor on our 2009 LE and it ran great for about 9 months. It's now back to the old habit of not wanting to move forward, especially when starting on an upward slope. We have 189k miles on it. I'm planning on replacing all of the solenoids, stepper motor, wiring harness, and filter this weekend, but I fear the valve body itself may have a section or two leaking internally that leads to these issues at higher miles.
 

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Discussion Starter · #3 ·
I'm afraid you may be right about the valve body... ironically, your car and hers are almost identical in mileage ; she has 190k on the clock.
I had her reset the code, and it's driving and "shifting" again, but it's got a stutter/hesitation in it that's random and appears to only happen either on deceleration or low load.
 

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Well, mine didn't go well. Saturday, I installed the new goodies, reassembled and the car wouldn't accelerate past about 2000 rpm. I tried driving around the block and it refused to go up a little hill. I had to reverse back onto another road and then it wouldn't go in reverse up that small incline, either. I pulled it back to the house and today I went through the process again to put back in the original wiring harness and solenoids but left the new stepper motor in. Put it back together and let the fluid seep back into all the nooks and crannies for a few hours. However, it has the same issues now and it cannot be driven at all now. It only goes a few miles per hour in either direction and barely makes it out of our driveway - maybe a 3% grade.
 

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I gave it another try and it got better but now I have neither low pull nor anything above about 50 mph. At least the rpms are higher and it doesn't appear to be in limp mode now. But it's not a great car in the hills of Eastern Tennessee...
 

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Discussion Starter · #6 ·
I gave it another try and it got better but now I have neither low pull nor anything above about 50 mph. At least the rpms are higher and it doesn't appear to be in limp mode now. But it's not a great car in the hills of Eastern Tennessee...
My girlfriend called me this morning and said she had a very similar event - she turned left onto a road, and the car wouldn't accelerate. She was doing maybe 5mph. She said that went on for a few minutes, and then it let go and accelerated normally. No SES light was tripped. This is one of the most bizarre cars I've ever worked on... btw, East TN here as well....
 

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My girlfriend called me this morning and said she had a very similar event - she turned left onto a road, and the car wouldn't accelerate. She was doing maybe 5mph. She said that went on for a few minutes, and then it let go and accelerated normally. No SES light was tripped. This is one of the most bizarre cars I've ever worked on... btw, East TN here as well....
Check the air intake hose for cracks. I had similar symptoms. Replaced the air intake hose and problem solved. Note, I couldn't see the cracks in the hose till I took it off.
 

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If you have an Android phone or tablet, buy and download the CVTz50 app and use an ELM 327 ODBII dongle to read the transmission codes. I did that today and there are several codes for the trans. Our might be done. Torque Pro and other apps won't see the Nissan CVT info.
 

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Discussion Starter · #10 ·
I don't unfortunately ; we moved to all iPhones at work a few years ago and I've not had a personal cell phone in 16 years lol
I think I have a few amazon fire tablets downstairs though.
 

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I don't unfortunately ; we moved to all iPhones at work a few years ago and I've not had a personal cell phone in 16 years lol
I think I have a few amazon fire tablets downstairs though.
Android phones can be found for cheap money, especially used.

I don't think CVTz50 will work with an Amazon Fire, it runs a modified Android OS -- see if the app installs on it...
 

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Discussion Starter · #12 ·
So after talking to her about it this morning, what appears to be happening is when she tries to pull out on an incline, the CVT isn't dropping into low range, it's staying high. There's no code being thrown. I'm about to order a full valve body for this thing, but how do I know what model valve body fits it without taking the trans apart and getting the part number directly off of it?
 

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Before jumping into replacing your valve body, I would drop the pan and inspect for wear debris and clean the internal mesh filter. If it's particularly clogged, consider replacing the external filter as well. This may restore fluid pressure. It also allows you to inspect the valve body.
 

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Discussion Starter · #14 ·
Before jumping into replacing your valve body, I would drop the pan and inspect for wear debris and clean the internal mesh filter. If it's particularly clogged, consider replacing the external filter as well. This may restore fluid pressure. It also allows you to inspect the valve body.
Already cleaned the filter and whatnot when I replaced the step motor a few weeks ago.
From a visual standpoint nothing looked out of the ordinary. The arm the stepper motor actuates moved freely. Internal filter didn't seem very dirty, but I cleaned it anyway.
Where do I get an external filter? I don't see a part listing for it at any of the major parts houses.
 

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I overlooked that you had mentioned doing the drain and fill...

The external filter is mentioned in this thread:

 

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DTC P1778 STEP MOTOR - FUNCTION PFP:31947

The step motor's 4 aspects of ON/OFF change according to the signal from TCM.
As a result, the flow of line pressure to primary pulley is changed and pulley ratio is controlled.
This diagnosis item detects when electrical system is OK, but mechanical system is NG.
____
Something binding? Bad step motor? Linkage connection or position?
 

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Discussion Starter · #17 ·
It finally threw another code, as it basically stopped. Threw a code for Pressure Solenoid A P0746. At this point I’m thinking the pressure relief valve is sticking. Gonna replace the valve with the transgo kit and replace the valve body for good measure.
 

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If you are talking about the flow control valve, which in essence is a pressure relief valve, to do it the transmission needs to be removed and the bell housing cover removed, then the fluid pump, they sure could have made it an easy deal to remove the pan and valve body, but they didn't.
Here is what I found on that code for a 2004 murano.
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Possible Cause
Line pressure control system
Output speed sensor (Secondary speed sensor)
Input speed sensor (Primary speed sensor)
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Flow control valve contributes to Line pressure control.
If it dumps too much fluid the line pressure drops.
---------------------------------------------
Also here is more.

DTC P0746 PRESSURE CONTROL SOLENOID A PERFORMANCE (LINE PRESSURE
SOLENOID VALVE)
Description
The pressure control solenoid valve A (line pressure solenoid valve) regulates the oil pump discharge pressure
to suit the driving condition in response to a signal sent from the TCM.
------------------------------------
And the reason for them mentioning the Output sensor and Input sensor is because the TCM uses those inputs to adjust the pressures.
So yes its important to have them working correctly.
Also make sure the valving that the Pressure control solenoid controls is free and not worn scored etc.
 

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Discussion Starter · #19 ·
Yep, that’s the one… I know what it takes to get to it, unfortunately. I agree they could’ve made it easier. I’m honestly tempted to just rebuild the thing if I’m already in that far…
 

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Some advice. There is some very tricky stuff during the rebuild process. Especially dealing with the variators, it is also a good idea to go with the pins instead of the balls in the variators. I ended up reusing the old variator piston seal rings since the replacements in the kit had horrible end laps that didn't want to seal very well at all. You will need a press to work on the variators. It is very easy during the install of the variator pistons to have them cock and do damage, like everything else bad design. Some videos show it as easy, nope. The forward and reverse clutches do not wear much. The transfer gear bearings are almost unobtainium you have to match them to similar bearings, that is if they are bad mine were. If it is out even the transfer case should be resealed, if it is similar to the 2004 model there is a very nasty internal seal that we made a special tool to install it, it requires a certain distance from the end of the shaft down in a so many inches or mm I forget the dimension.
 
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