* Low transmission fluid: Check the transmission fluid level and add more if necessary.
* Dirty transmission fluid: Change the transmission fluid and filter.
* Faulty shift solenoid: The shift solenoid is responsible for engaging the reverse gear. If it is faulty, it will need to be replaced.
* Faulty reverse gear: The reverse gear itself could be damaged or worn out. This will require a transmission rebuild.
To diagnose the problem, you will need to take your Pathfinder to a qualified mechanic. They will be able to determine the cause of the problem and recommend the best course of action.
