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Mechanical Inspection: Diagnosis

  1. Remove Heated Oxygen Sensor (HO2S) in front of catalytic converter. Install Backpressure Tester (J 35314-A) in place of HO2S. Start engine and allow it to reach normal operating temperature. Record the exhaust system backpressure reading. If backpressure does not exceed 1.25 psi (8.6 kPa), go to next step. If backpressure is more than 1.25 psi (8.6 kPa), go to step  3 .
  2. Increase engine speed to 2000 RPM and note backpressure. If reading exceeds 1.25 psi (8.6 kPa), go to next step. If reading does not exceed 1.25 psi (8.6 kPa), go to step  6 .
  3. Turn ignition switch to OFF position. Remove backpressure gauge and install HO2S. Remove post-catalyst HO2S and install backpressure gauge. Start engine and let idle. Note backpressure. Increase engine speed to 2000 RPM and note backpressure. If reading exceeds 1.25 psi (8.6 kPa), go to next step. If reading does not exceed 1.25 psi (8.6 kPa), go to step  5 .
  4. Check exhaust system for collapsed pipe, debris, heat distress, 2-layer exhaust pipe separation and possible internal muffler internal failure. Replace as necessary. After repair, go to  6 .
  5. Replace catalytic converter. After repair, go to next step.
  6. Remove the backpressure gauge and reinstall the HO2S sensor. Clear DTCs. Road test the vehicle in order to verify the repair.
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