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EC-304 < DTC/CIRCUIT DIAGNOSIS > [QR25DE] P0420 THREE WAY CATALYST FUNCTION P0420 THREE WAY CATALYST FUNCTION DTC Description INFOID:0000000011278026 DTC DETECTION LOGIC The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2. A three way catalyst (manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase. When the frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed. POSSIBLE CAUSE • Three way catalyst (manifold) • Exhaust tube • Intake air leaks • Fuel injector • Fuel injector leaks • Spark plug • Improper ignition timing FAIL-SAFE Not applicable DTC CONFIRMATION PROCEDURE 1. PRECONDITIONING If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test. 1. Turn ignition switch OFF and wait at least 10 seconds. 2. Turn ignition switch ON. 3. Turn ignition switch OFF and wait at least 10 seconds. YES >> GO TO 2. NO >> GO TO 6. 2. PERFORM DTC CONFIRMATION PROCEDURE-1 With CONSULT TESTING CONDITION: Do not hold engine speed for more than the specified minutes below. 1. Start engine and warm it up to the normal operating temperature. 2. Turn ignition switch OFF and wait at least 10 seconds. 3. Turn ignition switch ON. 4. Turn ignition switch OFF and wait at least 10 seconds. 5. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load. 6. Let engine idle for 1 minute. 7. Select “DATA MONITOR” mode of “ENGINE” using CONSULT. 8. Check that “COOLAN TEMP/S” indicates more than 70 °C (158°F). SEF484YB DTC No. CONSULT screen terms (Trouble diagnosis content) DTC detecting condition P0420 TW CATALYST SYS-B1 • Three way catalyst (manifold) does not operate properly. pacity. |