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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 (ALERO & Grand Am) >> 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.
WARNING: While engine is operating, the exhaust system will become extremely hot. To prevent burns avoid contacting a hot exhaust system.
  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. Remove the HO2S 2 located in front of and closest to the catalytic converter. Install the Exhaust Back Pressure Gauge (J 35314-A) in place of the AIR check valve or HO2S sensor. Start the engine. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 2 psi (14 kPa)? If yes, go to next step. If no, go to step  8.
  5. Turn ignition switch to LOCK position. Remove the exhaust back pressure gauge still installed increase and monitor engine speed to 2000 RPM. Re-install the AIR check valve/O2S. Remove the post-catalytst HO2S 2. Install the exhaust back pressure gauge in place of the HO2S 2. Start the engine. Increase and monitor the engine speed at 2000 RPM. Observe the exhaust system back pressure reading on the gauge. Does the reading exceed 2 psi (14 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. 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 and reinstall the AIR check valve or the HO2S. Using a scan tool, 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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