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Diagnostic Procedure

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  1. Verify the customers concern. Go to next step.
  2. Did you review the exhaust system check and perform the necessary inspections? If yes, go to next step. If no, see EXHAUST SYSTEM CHECK .
  3. Is the system equipped with dual exhaust? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
  4. Remove the HO2S that is in front of the catalytic converter. Install the Exhaust Back Pressure Gauge (J 35314-A), or equivalent, in place of the HO2S sensor. Start the engine. Increase and monitor the engine speed at 2500 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 1.25 psi (9 kPa)? If yes, go to next step. If no, go to step  8.
  5. Turn the engine off and place the ignition in LOCK position. Remove the exhaust back pressure gauge. Re-install the HO2S sensor. Remove the post-catalyst HO2S 2 sensor. Install the exhaust back pressure gauge in place of the post HO2S sensor. Start the engine. Increase and monitor the engine speed at 2500 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 1.25 psi (9 kPa)? If yes, go to next step. If no, go to step  7.
  6. Check the exhaust system for the following conditions:
    • Damage in the exhaust pipe.
    • Debris in the exhaust pipe.
    • Muffler or resonator internal failure.
    • Two-layer exhaust pipe separation.

    Repair as necessary. After repair, go to step  8.

  7. Replace the catalytic converter. After repair, go to next step.
  8. Remove the exhaust back pressure gauge. Reinstall the applicable HO2S sensor. Clear any codes. Road test the vehicle to verify the repair. Did you correct the condition? If yes, system is okay at this time. If no, go to step  2.
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