O2 Sensor And Catalytic Converter Test (HSN 0897-03)

O2 SENSOR AND CATALYTIC CONVERTER TEST

TECHNICAL SERVICE BULLETIN

SERVICE INFORMATION

On pre-OBD II vehicles that fail the State emissions test but do not set a DTC and do not have a driveability problem, test the O2 (oxygen) sensor and the catalytic converter with this procedure:

1. Run the engine until it warms up, then monitor O2 sensor voltage with the PGM Tester, or by backprobing the sensor.
   • If the voltage rapidly fluctuates between 0.2 and 0.8, the sensor and PGM-FI system are OK; go to step 2.
   • If the voltage is between 0.8 and 1.0, correct the causes of a rich mixture.
   • If the voltage is between 0 and 0.3, correct the causes of a lean mixture.
   • If the voltage is between 0.4 and 0.6, replace the sensor.
2. While the engine is idling, disconnect one of the fuel injector connectors, and monitor the tailpipe emissions with an exhaust analyzer.
   • If the emissions don't drop within 20 seconds, replace the catalytic converter. The cylinder with the disconnected injector acts as an air pump, injecting oxygen into the exhaust stream. If the catalytic converter is working, this action will lower tailpipe emissions.
   • If the emissions drop within 20 seconds, the catalytic converter is OK. Look for other causes of high emissions, such as a rich or lean mixture, a fouled plug, or a bad plug wire.