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Home › Lexus › 1998 › SC 300 › Repair and Diagnosis › Engine Performance › System › Engine Controls - Tests W/Codes › Diagnostic Tests › DTC P0420 Or P0430: Catalyst System › Confirmation Test (Using Oscilloscope)

Confirmation Test (Using Oscilloscope)

  1. To test banks No. 1 and 2 oxygen sensors No. 1, backprobing, connect oscilloscope between ECM E16 harness connector terminal No. 17 (White/Red wire) and terminals No. 12 (White wire) and No. 11 (Red/Blue wire). To test bank No. 1 and No. 2 oxygen sensors No. 2, backprobing, connect oscilloscope between ECM E16 connector terminal No. 17 (White/Red wire) and ECM E18 harness connector terminal No. 8 (White wire), and between ECM E16 harness connector terminal No. 17 (White/Red wire) and ECM E20 harness connector terminal No. 24 (Green wire).
  2. Ensure all accessories are turned off. Start and warm engine to operating temperature. Increase engine speed to 2500-3000 RPM for 3 minutes. Using oscilloscope, ensure heated oxygen sensors (bank 1 and 2 sensor 1 and 2) feedback to ECM fluctuates around .5 volt and are different from each other. See Figure.
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