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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0420 and/or P0430 is displayed, go to next step.
  2. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Check heated oxygen sensors No. 1 circuits. See DTC P0130 OR P0150: HEATED OXYGEN SENSOR NO. 1 CIRCUIT . If problem exists, repair as necessary. If problem does not exist, go to next step.
  4. Check heated oxygen sensor No. 2 circuits. See DTC P0136 OR P0156: HEATED OXYGEN SENSOR NO. 2 CIRCUIT . If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.
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