Engine “knock” may be heard on an applied vehicle just above engine idle speed (800-1,100 rpm) with the engine under a slight load. The noise cannot be detected over 1,100 rpm.

Applied Vehicles:
• 1999-2002 Frontier (D22) with VG33E; not supercharged.
• 2000-’02 Xterra (D22) with VG33E; not supercharged.

The cause may be a normal pulsating noise coming from the EVAP purge solenoid valve and piping (in the engine compartment) transferring into the passenger cabin. However, use the following procedure to reduce the noise.

Service Procedure:
1. Start and run the engine for at least one minute.

2. Use CONSULT-II to view the status of the “Closed Throttle Position Switch” (CTPS).

3. Set the Parking Brake, then perform the following;

• For vehicles with an automatic transmission, with your foot on the brake, place the A/T gear selector in “D.”
• For vehicles with a manual transmission, depress the clutch and select any gear.

4. While viewing CTPS status, open the th...