Overall Function Check

Use this procedure to check the overall function of the three way catalyst (manifold). During this check, a DTC might not be confirmed.

WITH GST 

1. Start engine and warm it up to the normal operation temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3, 500 and 4, 000 RPM for at least 1 minute under no load.
4. Let engine idle for 1 minute.
5. Set voltmeters probes between ECM terminals 50 [HO2S1 (bank 1) signal], 51 [HO2S1 (bank 2) signal] and engine ground, and ECM terminals 56 [HO2S2 (bank 1) signal], 57 [HO2S2 (bank 2) signal] and engine ground.
6. Keep engine speed at 2, 000 RPM constant under no load.
   Fig 1: Checking Voltage Between ECM Terminals 50 And 56 And Engine Ground

   Courtesy of NISSAN MOTOR CO., U.S.A.
   Fig 2: Checking Voltage Between ECM Terminals 51 And 57 And Engine Ground

   Courtesy of NISSAN MOTOR CO., U.S.A.
7. Make sure that the voltage switching frequency (high & low) between ECM terminals 56 and engine ground, or 57 and engine ground is very less than that of ECM terminals 50 and engine ground, or 51 and engine ground.

   Switching frequency ratio = A/B 

   A: Heated oxygen sensor 2 voltage switching frequency 

   B: Heated oxygen sensor 1 voltage switching frequency 

   This ratio should be less than 0.75. 

   If the ratio is greater than above, it means three way catalyst (manifold) does not operate properly. Go to "DIAGNOSTIC PROCEDURE ".