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2011 Altima stepper commanded wrong

967 Views 6 Replies 2 Participants Last post by  VStar650CL, 
Keineth
6
2011 Altima. My stepper motor goes up, hits 197 before 10 mph. I can't drive over 40 mph. After stepper motor is fully extended, the tcm never commands it to retract. I can reset the stepper motor and pressure readings are good until tcm commands the stepper motor out of wack.

P0746 and p0868. Took valvebody out cleaned it and solenoids while being actuated by 9v, have replaced flow control valve inside trans pump, along with both filters and all speed sensors, and stepper motor (granted with cheap Amazon),
Pictures aren't in order. Stepper target and actual goes up incrementally each time hitting the throttle, and stays commanded there even in park.
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VStar650CL
I don't think the stepper itself is causing your issue, you have no Primary pressure. PP should never be zero even in Park. The P0746 was the TCM detecting that it couldn't change gear ratios because the line pressure solenoid was stuck. This is the DTC description and detection parameter from the FSM:
Pressure Control Solenoid A Performance/Stuck Off - Unexpected gear ratio was detected in the low side due to excessively low line pressure

It probably isn't an electrical issue, that would most likely give you a P0745. For some reason Nissan never publishes failsafes for the CVT TCM's, but they usually stick in something like "3rd gear" when the TCM has a problem it can't deal with. I suspect that's what you're seeing with the stepper.
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Keineth
Thanks for your reply. As far as primary pressure, My valvebody only has one pressure switch... some jf011e come with 2. Some come with one, and rely on secondary pressure sensor only...
I dont think it's my step motor. As the actual number is in sync with commanded number by tcm...

My tcm for some reason doesn't retract StM.

I've took the solenoids out. Ohm tested, and actuated each one. None are physically stuck,
tho i haven't done a physical line pressure test on trans[/QUOTE]
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VStar650CL
Keineth said:
Thanks for your reply. As far as primary pressure, My valvebody only has one pressure switch... some jf011e come with 2. Some come with one, and rely on secondary pressure sensor only...
I dont think it's my step motor. As the actual number is in sync with commanded number by tcm...

My tcm for some reason doesn't retract StM.

I've took the solenoids out. Ohm tested, and actuated each one. None are physically stuck,
tho i haven't done a physical line pressure test on trans
Click to expand...
Yep, you're right, I just pulled the diagrams and the RE0F10A in '11 didn't have a PP sensor. My bad. P0746 is still a performance code and not a hardcode, the TCM is trying to tell you it can't find the right gear ratio even though it's running the stepper out to the stops. Can't be basic line pressure because your SP readings look okay. Are your speed sensors working? Or maybe there's a mechanical issue with the stepper mechanism?
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Keineth
Ive changed input, output on trans, as well as crank sensor on engine and stepper motor. Granted all were cheap Amazon replacements... the flow control valve was from superior.
Speed is registering through cvt app through all three options (abs,cvt,engine)
I think the speed sensors talk to the tcm, and the tcm talks to the step motor,

In the pics, there is a discrepancy with air intake temp.. which shouldnt be that high imo...

Is there a possibility that even though the solenoids actuated when 9 volts applied, that it's still getting stuck off? I'll be ok with purchasing a valve body if I'm able to return it for refund if problem persist.
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VStar650CL
I'm pretty sure VB's are non-returnable if you get one from Nissan, but maybe from a 3rd-party source. If it's a sensor issue then it's probably the Primary Speed sensor (the one on the front of the case) causing the issue. The Secondary Speed doesn't do anything when the car is stopped, but the TCM is always looking at the input shaft for slip revs.
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VStar650CL
Keineth said:
Is there a possibility that even though the solenoids actuated when 9 volts applied, that it's still getting stuck off? I'll be ok with purchasing a valve body if I'm able to return it for refund if problem persist.
Click to expand...
Only if something is physically wrong in the VB causing a leak or pressure loss, or making the shuttle bind.
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