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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1371 (Engine Exhaust System) >> Diagnostic Information and Procedures >> Restricted Exhaust >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. 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 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:  If high back pressure is not found at idle, increasing the engine speed may help find a restriction. Perform operational check before returning vehicle to customer.
  3. 6:  This step will isolate the catalytic converter from the remainder of the exhaust system.
  4. 9:  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 pre-converter HO2S that is in the exhaust manifold. Refer to Heated Oxygen Sensor Replacement - Position 1 (FWD) or Heated Oxygen Sensor Replacement - Position 1 (AWD) or Heated Oxygen Sensor Replacement - Position 1 .
  2. Install the J 35314-A  in place of the HO2S sensor. See Special Tools and Equipment  .
  3. Start and run the vehicle.
  4. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 8.6 kPa (1.25 psi) Go to Step 6 (LV6 Only)  Go to Step 5 
5 
  1. With the J 35314-A  still installed increase and monitor engine speed to 2000 RPM. See Special Tools and Equipment  .
  2. Observe the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 8.6 kPa (1.25 psi) Go to Step 7  System OK
6
  1. Turn the ignition Off and place the ignition in the lock position.
  2. Loosen the exhaust manifold to catalytic converter flange bolts.
  3. Start the vehicle.
  4. With the engine idling at normal operating temperature, record the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 8.6 kPa (1.25 psi) Go to Step 9  Go to Step 7 
7 
  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 pre-converter HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 1 (FWD) or Heated Oxygen Sensor Replacement - Position 1 (AWD) or Heated Oxygen Sensor Replacement - Position 1 .
  4. On all engines, remove the post-catalyst HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Position 2 (FWD) or Heated Oxygen Sensor Replacement - Position 2 (AWD) or Heated Oxygen Sensor Replacement - Position 2 .
  5. Install the J 35314-A  in place of the post HO2S sensor. See Special Tools and Equipment  .
  6. Start and idle the engine and monitor the engine speed to 2000 RPM.
  7. Observe the exhaust system back pressure reading on the gage.
Does the reading exceed the specified value?		 8.6 kPa (1.25 psi) Go to Step 8  Go to Step 10 
8 Inspect the exhaust system for the following conditions:
  • Damage in the exhaust pipe
  • Debris in the exhaust pipe
  • Muffler internal failure
  • 2-layer exhaust pipe separation

Did you find and correct the condition?		 - Go to Step 11  -
9 On LV6 engines, replace the exhaust manifold/catalytic converter assembly. Refer to Exhaust Manifold Replacement (2WD)  or Exhaust Manifold Replacement (AWD)  .
Did you find and correct the condition?		 - Go to Step 12  -
10 Replace the catalytic converter. Refer to Catalytic Converter Replacement (LV6 Engine)  or Catalytic Converter Replacement (LNK Engine)  .
Did you find and correct the condition?		 - Go to Step 12  -
11 Remove the J 35314-A  and reinstall the HO2S sensor. See Special Tools and Equipment  . Refer to Heated Oxygen Sensor Replacement - Position 2 (FWD) or Heated Oxygen Sensor Replacement - Position 2 (AWD) or Heated Oxygen Sensor Replacement - Position 2 .
Did you correct the condition?		 - Go to Step 12  Go to Step 2 
12 
  1. Clear any codes.
  2. 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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