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Home >> Chevrolet >> 2008 >> Optra LS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 1.6L >> Diagnostic Information and Procedures >> DTC P0135 or P0141 >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate H02S.
  2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 2 and ground.
      IMPORTANT: The ignition 1 voltage circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition 1 voltage circuit.
    • If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.
  3. Ignition OFF, connect a test lamp between the control circuit terminal 3 and B+. The test lamp should not illuminate.
    • If test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Engine running, verify the test lamp illuminates or flashes.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  5. If all circuits test normal, test or replace the H02S sensor.
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