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Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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  . 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 vehicle equipped with a 6.6 L diesel engine? - 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 (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 4.3L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 4.8L, 5.3L, and 6.0L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 8.1L.
  2. Install the J 35314-A  in place of the AIR check valve or HO2S sensor. See Special Tools and Equipment .
  3. Start the engine.
  4. Increase and monitor the engine speed at 2000 RPM.
  5. Observe the exhaust system back pressure reading on the gauge.
Does the reading exceed the specified value?		 20 kPa (3 psi)
If equipped with a 4.8L, 5.3L, or 6.0L - 3.4 kPa (0.5 psi)		 Go to Step 5  Go to Step 8 
5 
  1. Turn the engine off and place the ignition in the lock position.
  2. Remove the J 35314-A  . See Special Tools and Equipment .
  3. Re-install the AIR check valve/HO2S sensor. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 4.3L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 4.8L, 5.3L, and 6.0L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 1 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1 in Engine Controls - 8.1L.
  4. Remove the post-catalyst HO2S sensor. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in engine Controls - 4.3L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in Engine Controls - 4.8L, 5.3L, and 6.0L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in Engine Controls - 8.1L.
  5. Install the J 35314-A  in place of the post HO2S sensor.
  6. Start the engine.
  7. Increase and monitor the engine speed at 2000 RPM.
  8. Observe the exhaust system back pressure reading on the gauge.
Does the reading exceed the specified value?		 20 kPa (3 psi)
If equipped with a 4.8L, 5.3L, or 6.0L - 3.4 kPa (0.5 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 (4.3L, 4.8L, and 5.3L Engines)  or Catalytic Converter Replacement (6.0L and 8.1L Engines)  or Catalytic Converter Replacement (6.6L Engine) .
Did you find and correct the condition?		 - Go to Step 8  -
8 
  1. Remove the J 35314-A  . See Special Tools and Equipment .
  2. Reinstall the AIR check valve or the HO2S sensor. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in engine Controls - 4.3L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in Engine Controls - 4.8L, 5.3L, and 6.0L; Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 in Engine Controls - 8.1L.
  3. Clear any codes.
  4. 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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