Catalytic Converter: Testing and Inspection

Pressure Testing The Exhaust System at The Oxygen Sensor:

NOTE: Turbocharged engines are equipped with three catalytic converters and two oxygen sensors, which are threaded into the turbocharger assemblies. The following tests should be performed at each oxygen sensor port.


1. Carefully disconnect and remove the O2 sensor.
2. Install an Exhaust Backpressure Tester in place of the Oxygen sensor.
3. Start the engine and let it idle, note the reading on the backpressure gauge. The reading should not exceed 1.25 psi (8.6 kPa).
4. Increase the engine rpm to 2,000. The reading should not exceed 3 psi (20.7 kPa).
5. If the backpressure exceeds the given specifications, a restriction within exhaust system is indicated.
6. Inspect the exhaust system for a collapsed pipe, heat distress, internal muffler failure or a plugged or restricted catalytic converter.
7. After completing the tests, coat the oxygen sensor threads with an anti-seize compound before installing.