Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

1. Remove the front HO2S on the side of the engine that is suspected of being restricted. Refer to Heated Oxygen Sensor Replacement .
2. Install the Exhaust Back Pressure tester J 35314-A in place of HO2S.
3. Idle the engine at normal operating temperature.
4. Observe the exhaust system back pressure reading on the gauge.

Does the reading exceed the specified value?

8.6 kPa (1.25 psi)

Go to Step 4

Go to Step 3

1. The Exhaust Back pressure Gauge J 35314-A still installed.
2. Increase engine speed to 2000 RPM.
3. Observe the exhaust system back pressure reading on the gauge.

Does the reading exceed the specified value?

20.7 kPa (3 psi)

Go to Step 4

If a driveability symptom exists, refer to Symptoms

1. Turn OFF the engine.
2. Re-install the front HO2S.
3. Remove the rear HO2S sensor on the side of the engine that is suspected of being restricted. Refer to Heated Oxygen Sensor Replacement .
4. Install the Exhaust Back Pressure tester J 35314-A in place of the HO2S sensor.
5. Idle the engine.
6. Increase the engine speed to 2000 RPM.
7. Observe the exhaust system back pressure reading on the gauge.

Does the reading exceed the specified value?

20.7 kPa (3 psi)

Go to Step 5

Go to Step 6

1. Repair the restriction in the exhaust system after the Catalytic Converter.
2. Check the exhaust system for the following:

•	Collapsed pipe

•	Heat distress

•	Internal muffler failure

Is the action completed?

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System OK

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Replace Catalytic Converter. Refer to Intermediate Pipe Replacement in Engine Exhaust.

Is the action completed?

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System OK

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