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Test Description

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 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  . See Special Tools . Removing the heated oxygen sensor (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 6.6L diesel engine? - Go to Diagnostic Aids Go to Step 4 
4 
  1. Remove the HO2S that is in front of and closest to the catalytic converter. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.3L engine, or to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (2500 Series - Cab/Chassis) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (2500 Series - Cab/Chassis) for the 4.8L, 5.3L, 6.0L, and 6.2L engines.
  2. Install the J 35314-A  Exhaust Back Pressure Gage in place of the HO2S. See Special Tools .
  3. Start the engine.
  4. Increase and monitor the engine speed at 2,000 RPM.
  5. Observe the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 20 kPa (3 psi)
If equipped with a 4.8L, 5.3L, 6.0L, or 6.2L - 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 .
  3. Re-install the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for the 4.3L engine, or to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (2500 Series - Cab/Chassis) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (2500 Series - Cab/Chassis) for the 4.8L, 5.3L, 6.0L, and 6.2L engines.
  4. Remove the post-catalyst HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.3L engine, or to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (2500 Series - Cab/Chassis) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (2500 Series - Cab/Chassis) for the 4.8L, 5.3L, 6.0L, and 6.2L engines.
  5. Install the J 35314-A  in place of the post HO2S. See Special Tools .
  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 gage.
Does the reading exceed the specified value?		 20 kPa (3 psi)
If equipped with a 4.8L, 5.3L, 6.0L, or 6.2L - 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)  or Catalytic Converter Replacement (4.8L, 5.3L, 6.0L, 6.2L)  or Catalytic Converter Replacement (6.6L)  or Catalytic Converter Replacement - Left Side (6.0L - Cab/Chassis) .
Did you find and correct the condition?		 - Go to Step 8  -
8 
  1. Remove the J 35314-A  . See Special Tools .
  2. Reinstall the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for the 4.3L engine, or to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (2500 Series - Cab/Chassis) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (1500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (2500 Series) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (2500 Series - Cab/Chassis) for the 4.8L, 5.3L, 6.0L, and 6.2L engines.
  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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