DTC 33: Front Heated Oxygen Sensor (Ho2S)

1. Check Input Signal Circuit
   
   Turn ignition off. Disconnect HO2S harness connector and ECM harness connector. See Figure and Fig 1 . Verify harness continuity between ECM connector terminal No. 46 and HO2S connector terminal "B" (White wire). See Fig 2 . Continuity should be present. Check for continuity between ECM connector terminal No. 46 and ground. Continuity should not be present. If continuity is as specified, go to next step. If continuity is not as specified, repair harness or connectors as necessary.
2. Check Component
   
   Turn ignition off. Disconnect front HO2S wiring harness connector. Measure resistance between terminals "A" and "C". See Fig 3 . Check for continuity between terminals "A" and "B" and between terminals "B" and "C". Continuity should not be present. Replace HO2S if not as specified. If HO2S is okay, go to next step.
3. Loosen and retighten engine ground screws. Disconnect and reconnect wiring harness connector. Disconnect ECM and HO2S wiring harness connector. Check terminals for damage or corrosion. Repair if necessary and perform FINAL CHECK. If fault is still present, replace front HO2S sensor.

Fig 1: Locating Front HO2S Harness Connector (G20)

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

Fig 2: DTC 33, Checking Input Signal Circuit (G20)

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

Fig 3: DTC 33, Checking HO2S (G20)

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