Overall Function Check

Use this procedure to check the overall function of the three way catalyst. During this check, a 1st trip DTC might not be confirmed.

WITH GST 

1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch OFF and wait at least 5 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 RPM for 1 minute under no load.
4. Let engine idle for 1 minute.
5. Set voltmeters probes between ECM terminals 50 (Heated oxygen sensor 1 signal), 56 (Heated oxygen sensor 2 signal) and engine ground.
6. Keep engine speed at 2,000 RPM constant under no load.
7. Make sure that the voltage switching frequency (high & low) between ECM terminal 56 and engine ground is much less than that of ECM terminal 50 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 .

Fig 1: Setting Voltmeters Probes Between ECM Terminals And Engine Ground

Courtesy of NISSAN MOTOR CO., U.S.A.