LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2003 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 88 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) Or DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2) >> Diagnosis & Repair
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 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 sensor (bank 1, 2 sensor 1) circuits. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - LX470 article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  4. Check heated oxygen sensor (bank 1, 2 sensor 2). See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - LX470 article. If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.
scientia non olet · About LEMON Manuals