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Home >> Infiniti >> 2003 >> G35 2D Coupe, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls System - DTCS P0171 Through P0456 - Coupe >> DTC P0420, P0430: Three Way Catalyst Function >> Overall Function Check >> With GST

With GST

  1. Turn ignition switch OFF and wait at least 10 seconds.
  2. Start engine and keep the engine speed between 3, 500 and 4, 000 rpm for at least 1 minute under no load.
  3. Let engine idle for 1 minutes.
  4. Open engine hood.
  5. Set voltmeters probes between ECM terminals 35 [HO2S1 (bank 1) signal], 16 [HO2S1 (bank 2) signal] and engine ground, and ECM terminals 74 [HO2S2 (bank 1) signal], 55 [HO2S2 (bank 2) signal] and engine ground.
  6. Keep engine speed at 2, 000 rpm constant under no load.
    Fig 1: Testing Voltage Between ECM Terminals 35, 16 And Engine Ground
    G03583175Courtesy of NISSAN MOTOR CO., U.S.A.
  7. Make sure that the voltage switching frequency (high & low) between ECM terminals 74 and engine ground, or 55 and engine ground is very less than that of ECM terminals 35 and engine ground, or 16 and engine ground.

    Switching frequency ratio = A/B 

    1. A: Heated oxygen sensor 2 voltage switching frequency
    2. 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 1 does not operate properly. Go to "DIAGNOSTIC PROCEDURE ".

    Fig 2: Checking Heated Oxygen Sensor Voltage Switching Frequency (Voltage)
    G03583176Courtesy of NISSAN MOTOR CO., U.S.A.
NOTE: If the voltage at terminal 35 or 16 does not switch periodically more than 5 times within 10 seconds at step  7, perform trouble diagnosis for DTC P0133, P0153 first. (See DTC P0133, P0153 HO2S1 .)