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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 383 (Engine Controls - System & Component Testing - 3.4L) >> Exhaust System >> Restricted Exhaust (Impala & Monte CARLO) >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you verify the customers complaint? If yes, go to next step.
  2. Did you review the exhaust symptoms diagnostic information and perform the necessary inspections? If yes, go to next step. If no, go to SYMPTOM DIAGNOSIS - ENGINE EXHAUST under SYMPTOMS in TROUBLE SHOOTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article.
  3. Is the system equipped with dual exhaust? If yes, go to DIAGNOSTIC AIDS . If no, go to next step.
    4. WARNING: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.
  4. Remove the pre-catalyst Heated Oxygen Sensor 1 (HO2S 1). Install the Exhaust Back Pressure Gauge (J 35314-A) in place of the HO2S 1. Start and run the vehicle. 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 switch in LOCK position. Remove the exhaust back pressure gauge. Install the pre-catalyst HO2S 1. Remove the post-catalyst HO2S 2. Install the exhaust back pressure gauge in place of the post HO2S 2. 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.

    Did you find and correct the condition? If yes, go to step  8.

  7. Replace the catalytic converter. After repair, go to next step.
  8. Remove the exhaust back pressure gauge. Install the post-catalyst HO2S 2. 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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