Symptom:

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.

Vehicle moves forward or backward when selecting N position .

CHECK PNP SWITCH CIRCUIT
With CONSULT-II

Does TCM INPUT SIGNALS in DATA MONITOR show damage to PNP switch circuit?

Fig 1: Checking Park/Neutral Position Switch Circuit
Courtesy of NISSAN MOTOR CO., U.S.A.

Without CONSULT-II

Does self-diagnosis show damage to PNP switch circuit?

Yes or No
1. Yes: Check PNP switch circuit. Refer to DTC P0705 PARK/NEUTRAL POSITION (PNP) SWITCH .
2. No: GO TO 2.
CHECK CONTROL CABLE
Check control cable. Refer to CONTROL CABLE ADJUSTMENT .

Fig 2: Locating Control Cable
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG
1. OK: GO TO 3.
2. NG: Adjust control cable. Refer to CONTROL CABLE ADJUSTMENT .
CHECK A/T FLUID LEVEL
Check A/T fluid level again.

Fig 3: Checking Automatic Transaxle Fluid Level
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG
1. OK: GO TO 4.
2. NG: Refill ATF.
CHECK A/T FLUID CONDITION
1. Remove oil pan.
2. Check A/T fluid condition.
  
  Fig 4: Checking Automatic Transaxle Fluid Condition
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG
1. OK: GO TO 5.
2. NG:
  1. Disassemble A/T.
  2. Check the following items:
  - Forward clutch assembly
  - Overrun clutch assembly
  - Reverse clutch assembly
CHECK SYMPTOM
Check again.

OK or NG
1. OK: INSPECTION END
2. NG:
  1. Perform TCM input/output signal inspection.
  2. If NG, recheck TCM pin terminals for damage or loose connection with harness connector.