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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 190 (ENGINE EXHAUST SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESRESTRICTED EXHAUSTTEST DESCRIPTION
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Test Description

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Test Description
WARNING: This page is about a different car, the 2008 Cadillac STS. 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  Exhaust Back Pressure Gage. See Special Tools . Removing the heated oxygen (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 heated oxygen sensor (HO2S) that is in front of the catalytic converter. Refer to the appropriate procedure:
  2. Install the J 35314-A  Exhaust Back Pressure Gage in place of the HO2S sensor. See Special Tools .
  3. Start the engine.
  4. Increase and monitor the engine speed at 2,500 RPM.
  5. Observe the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 9 kPa (1.25 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 sensor. Refer to the appropriate procedure:
  4. Remove the post-catalyst HO2S sensor. Refer to the appropriate procedure:
  5. Install the J 35314-A  in place of the post HO2S sensor. See Special Tools .
  6. Start the engine.
  7. Increase and monitor the engine speed at 2,500 RPM.
  8. Observe the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 9 kPa (1.25 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 the appropriate procedure:
Did you find and correct the condition?		 - Go to Step 8  -
8 
  1. Remove the J 35314-A  . See Special Tools .
  2. Reinstall the applicable HO2S sensor. Refer to the following:
  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 
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.