For 1990-2009 cars

#### Special Tools

EN-35314-A Exhaust Back Pressure Gage

For equivalent regional tools. Refer to Special Tools.

### Diagnostic Aids

A quick check of exhaust flow will help determine for gasoline engines.

For the diesel engines with particulate filter the backpressure is measured by the exhaust pressure differential sensor. Refer to Exhaust Particulate Filter System Description

A scan tool can be used to initiate a controlled service mode DPF regeneration. Refer to Exhaust Particulate Filter Cleaning.

### Test Description

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

1. 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 gage .

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

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

3. 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 |

1. Remove the heated oxygen sensor 1. Refer to Heated Oxygen Sensor Replacement - Sensor 1.
2. Install the EN-35314-A gage in place of the heated oxygen sensor 1.
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?

14 kPa (2 psi)

Go to Step 4

Go to Step 7

4 |

1. Turn the engine off and place the ignition in the lock position.
2. Remove the EN-35314-A gage .
3. Install the heated oxygen sensor 1. Refer to Heated Oxygen Sensor Replacement - Sensor 1.
4. Remove the heated oxygen sensor 2. Refer to Heated Oxygen Sensor Replacement - Sensor 2.
5. Install the EN-35314-A gage in place of the heated oxygen sensor 2.
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?

--

Go to Step 5

Go to Step 6

5 | 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 7

--

6 | Replace the catalytic converter. Refer to Catalytic Converter Replacement. Did you find and correct the condition? | -- | Go to Step 7 | --
7 |

1. Remove the EN-35314-A Exhaust Back Pressure Gage .
2. Install the heated oxygen sensor 2. Refer to Heated Oxygen Sensor Replacement - Sensor 2.
3. Clear any DTCs.
4. Road test the vehicle in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2