Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota Tacoma. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.

For diagnosis and repair procedure, see Fig 1.

To check A/F sensor and oxygen sensor heater, see Fig 2 & Fig 3 .

For diagnosis of A/F sensor (B1 S1) function, see DTC P2195 & DTC P2196: OXYGEN (A/F) SENSOR CIRCUIT (BANK 1 SENSOR 1) .

For diagnosis of HO2S (B1 S2) function, see DTC P0136: OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2) .

For removal and installation of components, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

Fig 1: DTC P0420 Diagnostic Procedure

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Fig 2: Testing A/F Sensor Heater

Fig 3: Testing HO2S Heater