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Vehicle moves forward

Vehicle does not go backwards.

Vehicle throws codes related to accelerator pedal position sensor.

I didn't work on that so I am stupified.

I have checked the service manual and it seems to me that two things could be responsible for this state of affairs.

  1. Failure to replace transmission lip seal

  2. Failure to reprogram the TCM

Are these ideas on the mark?

Any and all advice would be appreciated.

BACKSTORY

It all started with a P1777 DTC. Nissan Rogue Factory Manual P1777 DTC definition and description

I ran the gamut of tests specified and arrived at the conclusion that the stepper motor was indeed bad.

CVT Stepper Motor - How it works

So it was determined that replacing the stepper motor would be the way to go, and so it was replaced.

But the DTC P1777 did not go away.

This goes against the grain of Nissan Motor Company to replace the entire valve body in the event of a stepper Motor failure

Resolution to P1777 DTC

So next the entire valve body was replaced as suggested by Nissan

But P1777 did not go away.

That raises a few questions:

The service manual wanted the lip seal to be taken down as part of disassembly and also reinstalled as part of reassembly, see pictures below:

Remove the lip seal instruction

Install the lip seal instruction

Note that the instruction is silent on replacing the old lip seal with a new lip seal, which makes the requirement to remove and reinstall the lip seal appear superfluous, unlike in the related but upgraded transmission with very similar characteristics in which the instructions were patently clear, remove the old lip seal and replace with a new lip seal

Instruction to replace lip seal during reassembly

For those who do not know, this is the only information I could find on the open internet on the role of lip seals in transmissions

Automatic Transmission Seals

If you take the time to read up the link above, you will appreciate that

Automatic transmission seals are used to contain pressure and prevent leakage.

When we compare that with this other quote from a third party repair manual for the very same transmission in question, it seems that the problem is hydraulic, and is linked to pressure losses

Third Party Repair Manual position on the lack of reverse operation

This extract describes the operation of the vehicle in reverse. The question is this? Is it that the forward clutch is not released? Is it that the reverse brake is not engaged?

Reverse Operation Described

If you carefully study the pictures of the location of the lip seal in question, it seems to match the picture of the Reverse apply in the following picture!

Is the location of the lip seal the same as the location of reverse apply and could that be why it is recommended to replace the lip seal?

It is instructive to note that after replacing the valve body the vehicle attempted to reverse then got stuck and stopped reversing!

CVT operation diagram

That is the detailed backstory...so the question the lack of reverse is it attributable to the non-replacement of the lip seal or is it connected to TCM initialization after valve body replacement?

  • Did you check the harness and connectors as suggested in the ‘possible causes’? – HandyHowie Oct 6 '18 at 20:39
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    As to the lip seal, in the installation picture the black circle with an X means DO NOT REUSE. The grease gun looking thing with the P means to lube the seal before installation. There is a probably a legend in your service manual you missed. I'd suggest if the seal wasn't replaced you hook up a scantool and line pressure gauge, check to see what the TCM wants to happen and what's happening as far as pressure goes. I'm unsure about your initialization question. There is a calibration that needs to be done after replacing the valve body. Can you link to the discussion? – Ben Oct 7 '18 at 4:39
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    Performing a TCM Calibration/Initialization shouldn't throw these APP codes and are I would think on separate circuits. I'd confirm APP supply voltage and signal to and from the PCM. – Ben Oct 7 '18 at 4:51
  • @HandyHowie: Harness is in perfect condition. triple checked – ElectronicsNewbie Oct 12 '18 at 3:57
  • @Ben You are right about the DO NOT REUSE. Just that it wasn't plain. This is the link that I am referring to certifiedtransmission.wordpress.com/2013/07/11/…. Called in external help and I think the problem has been resolved will post an answer soon. I never did perform a TCM Calibration/Initialization, my question was not performing one could it cause that, but the question is no longer relevant, it has been fixed – ElectronicsNewbie Oct 12 '18 at 3:59
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I have not independently verified the below, but I have been told this is the problem.

I explain the answer in pictures.

The following pictures are instructiveImage showing CVT operation - note especially the Shift link connecting the Primary and Secondary pulley to the stepper motor

Note the manual valve

Note the linkage in this picture

The shift link, manual valve or linkage may be wrongly installed and may lead to this sort of problem.

See a picture of it culled from the internet

Wrong install

Correct install

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