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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 40 (Engine Controls - Self-Diagnostics - 2.5) >> Diagnostic Tests >> DTC P1143: Front Heated Oxygen Sensor Lean Shift Monitoring >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition off. Loosen and retighten engine ground bolts. See Figure and Figure . Loosen and retighten HO2S to 30-37 ft. lbs. (40-50 N.m). Go to next step.
  2. Start engine and warm engine to normal operating temperature. Turn ignition off. Disconnect MAF sensor harness connector. Start engine and let it idle for at least 5 seconds. Turn ignition off and reconnect MAF sensor harness connector. Go to next step.
  3. Ensure first trip DTC P0102 is set. Clear DTCs. Start engine and let it idle for at least 10 minutes. Recheck for DTCs. If DTC P0171 is present and engine is hard to start, perform diagnosis for DTC P0171. See DTC P0171 OR DTC P0712 . If DTC P0171 is not present and engine is not hard to start, go to next step.
  4. Turn ignition off. Disconnect front HO2S harness connector. See Figure for component side view. Measure resistance between HO2S terminals. See HO2S HEATER RESISTANCE SPECIFICATIONS  for terminal selection. If HO2S does not test as specified, replace HO2S. Perform DTC CONFIRMATION TEST  to verify repair. If HO2S tests as specified, go to next step.
  5. Reconnect all harness connectors. Start engine and warm to normal operating temperature. Measure voltage between ground and ECM terminal No. 92 (White/Green wire) by backprobing. See Figure. Increase engine speed to 2000 RPM. The following conditions should exist:
    • Voltage cycles from 0-0.3 volt to 0.6-1.0 volt and back more than 5 times within 10 seconds.
    • Maximum voltage is more than 0.6 volt at least once.
    • Minimum voltage is less than 0.3 volt at least once.
    • Voltage never exceeds 1 volt.
    CAUTION: DO NOT reuse any HO2S that has been dropped from a height of 20" (.5 m) or more onto a hard surface such as concrete.

    If operation is as specified, go to next step. If operation is not as specified, replace HO2S. Perform DTC CONFIRMATION TEST  to verify repair.

  6. Check for intermittent condition. See INTERMITTENTS in TROUBLESHOOTING - NO CODES article. Perform DTC CONFIRMATION TEST  to verify repair.
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