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Home › Lexus › 1998 › LS 400 › 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 bank No. 1 and 2 oxygen sensors No. 1, backprobing, connect oscilloscope between ECM E13 connector terminal No. 17 (White/Black wire) and terminals No. 12 (Black wire) and No. 11 (White wire). To test bank No. 1 and 2 oxygen sensors No. 2. Backprobing, connect oscilloscope between ECM E13 connector terminal No. 17 (White/Black wire) and ECM E11 connector terminals No. 18 (Green wire) and No. 27 (Yellow wire).
  2. Ensure all accessories are turned off. Start and warm engine to normal 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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