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Home >> Buick >> 2015 >> Regal GS, 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  gauge.

    Removing the 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.

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. Refer to Heated Oxygen Sensor Replacement - Sensor 1 , for the 2.0L engine or Heated Oxygen Sensor Replacement - Sensor 1 for the 2.4L engine.
  2. Install the J-35314-A  Exhaust Back Pressure Gauge in place of the HO2S sensor.
  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 gauge.
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  gauge.
  3. Reinstall the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Sensor 1 , for the 2.0L engine or Heated Oxygen Sensor Replacement - Sensor 1 for the 2.4L engine. .
  4. Remove the post-catalyst HO2S sensor. Refer to the appropriate procedure. Refer to Heated Oxygen Sensor Replacement - Sensor 2 , for the 2.0L engine or Heated Oxygen Sensor Replacement - Sensor 2 for the 2.4L engine.
  5. Install the J-35314-A  gauge in place of the post HO2S sensor.
  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 gauge.
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:
  • Secondary catalytic converter restricted
  • 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 (LTG) Catalytic Converter Replacement (LUK, LEA) .
Did you find and correct the condition?		 - Go to Step 8  -
8 
  1. Remove the J-35314-A  gauge.
  2. Reinstall the applicable HO2S sensor. Refer to the appropriate procedure:
  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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