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Home >> Infiniti >> 2004 >> Q45 >> Repair and Diagnosis >> Engine Performance >> Engine Control System >> DTC P0139, P0159: Ho2S2 >> Overall Function Check >> With GST
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With GST

  1. Start engine and warm it up to the normal operating 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 voltmeter probes between ECM terminal 123 [HO2S2 (B1) signal] or 124 [HO2S2 (B2) signal] and ground.
  6. Check the voltage when revving up to 4,000 RPM under no load at least 10 times.

    (Depress and release accelerator pedal as soon as possible.)

    A voltage change should be more than 0.06V for 1 second during this procedure. 

    If the voltage can be confirmed in step 6, step 7 is not necessary. 

    Fig 1: Checking Voltage between ECM terminal 123 [HO2S2 (B1) signal] or 124 [HO2S2 (B2) signal] & ground
    G00760776Courtesy of NISSAN MOTOR CO., U.S.A.
  7. Keep vehicle at idling for 10 minutes, then check the voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in D position.

    A voltage change should be more than 0.06V for 1 second during this procedure. 

  8. If NG, go to Diagnostic Procedure  .