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Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota Tundra. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: This DTC uses two-trip detection logic. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected. To aid in diagnosis of deteriorated catalyst, it is recommended to perform Confirmation Engine Racing Pattern while observing HO2S waveform pattern. See CONFIRMATION ENGINE RACING PATTERN .

For diagnosis and repair procedure, see Fig 1. For A/F sensor heater test, see Fig 2. For HO2S heater test, see Fig 3.

For testing of systems or components, see SYSTEM & COMPONENT TESTING - V6 & V8 article. For removal and installation of components, see REMOVAL & INSTALLATION - V6 & V8 article.

Fig 1: DTC P0420 Diagnostic Procedure
G00238946Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 2: Testing Heater On A/F Sensor
G99C08733Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Fig 3: Testing Heater On Heated Oxygen Sensor
G00023084Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002