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Home › Pontiac › 2004 › Aztek Base, AWD › Repair and Diagnosis › Engine Mechanical › Engine Exhaust System › Diagnostic Information and Procedures › Restricted Exhaust › Test Description

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 4:  The exhaust system has very low back pressure under normal conditions. If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the J 35314-A  . See Special Tools and Equipment . Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
  2. 5:  This step will isolate the catalytic converter from the remainder of the exhaust system.
  3. 8:  Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to Step 2 and repeat diagnostic procedure on the opposite exhaust pipe.
Restricted Exhaust

Step Action Value(s) Yes No
1 Did you verify the customers complaint? - Go to Step 2  -
2 Did you review the exhaust symptoms diagnostic information and perform the necessary inspections? - Go to Step 3  Go to Symptoms - Engine Exhaust 
3 Is the system equipped with dual exhaust? - Go to Diagnostic Aids Go to Step 4 
4 
  1. Remove the AIR check valve or the HO2S that is in front of and closest to the catalytic converter. Refer to Heated Oxygen Sensor Replacement - Position 1 in Engine Controls - 3.4 L.
  2. Install the J 35314-A  Exhaust Back Pressure Gauge in place of the AIR check valve or HO2S sensor. See Special Tools and Equipment .
  3. Start the engine.
  4. Observe the exhaust system back pressure reading on the gauge.
Does the reading exceed the specified value?		 14 kPa (2 psi) Go to Step 5  Go to Step 8 
5 
  1. Turn OFF the engine and place the ignition in the lock position.
  2. Remove the J 35314-A  still installed increase and monitor engine speed to 2,000 RPM. See Special Tools and Equipment .
  3. Re-install the AIR check valve/HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 1 in Engine Controls - 3.4 L.
  4. Remove the post-catalytst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 in Engine Controls - 3.4 L.
  5. Install the J 35314-A  in place of the post HO2S sensor. See Special Tools and Equipment .
  6. Start the engine.
  7. Increase and monitor the engine speed at 2,000 RPM.
  8. Observe the exhaust system back pressure reading on the gauge.
Does the reading exceed the specified value?		 14 kPa (2 psi) Go to Step 6  Go to Step 7 
6 Inspect 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?		 - Go to Step 8  -
7 Replace the catalytic converter. Refer to Catalytic Converter Replacement .
Did you find and correct the condition?		 - Go to Step 8  -
8 
  1. Remove the J 35314-A  and reinstall the AIR check valve or the HO2S sensor. See Special Tools and Equipment . Refer to Heated Oxygen Sensor Replacement - Position 2 in Engine Controls - 3.4 L.
  2. Clear any codes.
  3. Road test the vehicle in order to verify the repair.
Did you correct the condition?		 - System OK Go to Step 2 
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