P0840 NISSAN -

Question

WHEN I START MY CAR AND PUT IT IN DRIVE IT GOES VERY SLOW

Answer 1

P0840 NISSAN - Transmission Fluid Pressure Sensor A

- Transmission Fluid Pressure Sensor A harness is open or shorted 
- Transmission Fluid Pressure Sensor A poor electrical connection 
- Faulty Transmission Fluid Pressure Sensor A 
- Transmission Valve Body

 

There is a service bulletin thats suggests replacing the transmission valve body. 
You can also check to see if it is covered under warranty. Nissan has extended the CVT warranty from 5 years/60,000 to 10 years/120,000 miles on some models 

https://www.autocodes.com/uploads/nissan/NTB09-148a.pdf