Oil Pressure Check

WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

WARNING:

Be careful not to burn yourself, as engine oil may be hot.
For M/T models, put the gearshift lever in the Neutral "N" position. For A/T models, put the selector lever in the Park "P" position.

Check the oil level.
Disconnect oil pressure switch harness connector.
Remove oil pressure switch.
Install the pressure gauge.
Start the engine and warm it up to normal operating temperature.
Check oil pressure with engine running under no-load.

Fig 1: Oil Pressure Specification Table
Courtesy of NISSAN MOTOR CO., U.S.A.

If difference is extreme, check oil passage and oil pump for oil leaks.

Fig 2: Identifying Oil Pressure Gauge
Courtesy of NISSAN MOTOR CO., U.S.A.
After the inspections, install the oil pressure switch as follows:
1. Remove the old sealant adhering to switch and engine.
2. Apply thread sealant and tighten the oil pressure switch to specification.
  Use Genuine High Performance Thread Sealant, or equivalent. Refer to RECOMMENDED CHEMICAL PRODUCTS AND SEALANTS .
  1. Oil pressure switch : 13 - 17 N.m (1.25 - 1.75 kg-m, 9 - 12 ft-lb)