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Restricted Exhaust

Restricted Exhaust


Special Tools

EN 35314-A Exhaust Back Pressure Gauge.

For equivalent regional tools, refer to Special Tools .

Diagnostic Aids

Refer to Hot Exhaust System Warning .

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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 EN 35314-A gauge.

Removing the HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.

5

This step will isolate the catalytic converter from the remainder of the exhaust system.

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 - Bank 1 Sensor 1 (LF1) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (LF1) .

2. Install the EN 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 EN 35314-A gauge.

3. Reinstall the HO2S sensor. See Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (LF1) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (LF1) .

4. Remove the post-catalyst HO2S sensor. Refer to the appropriate procedure. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (LF1) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (LF1) .

5. Install the EN 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:
• 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 - Left Side (LF1) or Catalytic Converter Replacement - Right Side (LF1) . Did you find and correct the condition? - Go to Step 8 -
8

1. Remove the EN 35314-A gauge.

2. Reinstall the relevant HO2S sensor. See Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (LF1) or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (LF1) .

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