For 1990-2009 cars

#### Tools Required

J 35314-A Exhaust Back Pressure Gauge

### Diagnostic Aids

Caution: Refer to Hot Exhaust System Caution in the Preface section.

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.

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 J 35314-A .

   Removing the heated oxygen sensor may set a DTC. When finishing this diagnostic table all codes must be cleared.

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.

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 pre-catalytic converter heated oxygen sensor (HO2S) that is in front of and closest to the catalytic converter. Refer to the appropriate procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for 3.6L engine.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for 6.0L engine.

2. Install the J 35314-A in place of the pre-catalytic converter heated oxygen sensor (HO2S).
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 4

Go to Step 7

4 |

1. Turn the engine off and place the ignition in the OFF position.
2. Remove the J 35314-A .
3. Re-install the pre-catalytic converter heated oxygen sensor (HO2S). Refer to the appropriate procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for 3.6L engine.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 for 6.0L engine.

4. Remove the post-catalytic converter heated oxygen sensor (HO2S). Refer to the appropriate procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for 3.6L engine.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for 6.0L engine.

5. Install the J 35314-A in place of the pre-catalytic converter heated oxygen sensor (HO2S).
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 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 - Left Side, Catalytic Converter Replacement - Right Side. Did you find and correct the condition? | -- | Go to Step 7 | --
7 |

1. Remove the J 35314-A .
2. Re-install the applicable heated oxygen sensor (HO2S). Refer to the appropriate procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for 3.6L engine.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 for 6.0L engine.

3. If re-programming is required. Refer to Control Module References.
4. Clear any codes.
5. Road test the vehicle in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2