2015 Nissan Sentra CVT problem

Derrick Diagnostician Kentucky Posted   Latest   Edited  
Unsolved
Drivetrain
2015 Nissan Sentra Advance 1.8L (MRA8DE)
P0846 — Transmission Fluid Pressure Sensor/Switch "B" Circuit Range/Performance
Rpms Fluctuating

Recently replaced CVT on this vehicles with used CVT a 20,000 mi on this CVT. Cleared calibration data relearn calibration data reset CVT fluid degradation interval. 2 weeks later vehicle has retired with the severe RPM fluctuations while driving seeming like CVT is hunting for position. Initially with no codes. Attempted calibration reset process again and have set code p0846 this is pressure rationality code fluid pressure sensor the b. Still have same symptom. In the beginning stages of learning how to diagnose these transmissions wonder if anyone had any tips for me thanks.

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Brandon Diagnostician
Arizona
Brandon
 

Was the tcm programming done ? Also if this one has a cooler was it flushed?

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Derrick Diagnostician
Kentucky
Derrick
 

did not reprogram tcm did preform service functions (cleared calibration data, relearned fluid degradation ) this is all manual requires after trans assembly replacement. Is this something you guys do though? Also relearned gear box clutch point learning. not sure but i will find out about flush i did not do the work another tech did just plying cleanup crew on this one.

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Brandon Diagnostician
Arizona
Brandon
 

Love doing clean up. I know that the TCM has to matched to the replacement trans. Everything else you did is correct procedure. After the programming you will have to do all the relearns , idle , gearbox ect. If the flush wasn't done that could effect the pressures.

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Paul Owner/Technician
California
Paul
 

I have no experience myself, but from reading the service information (which is a little hard to parse) it looks like P0846 will set if the difference between “Actual secondary pressure” and "Target secondary pressure" is greater than 0.675 MPA, OR, the Secondary pressure control valve solenoid is drawing more than 750mA. The only tests I found were to clear the code and see if it resets and…

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Tanner Diagnostician
Kansas
Tanner
   

Ran into this on same vehicle after i programed tcm. Turns out the r&r guy had switched the oss and iss as the connectors are the same. In the tcm data the vehicle speed was reading like a iss ie the pids for vss was 30mph in park and 0 when in drive at stop. Funny thing is it never threw a speed sensor code just a p0868 and p0846. The auxillary gearbox learn has to be done 3times? to…

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Thanks