Ответ: Горит чек.
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DTC P0420: Catalyst System Efficiency below Threshold
Circuit Description
ECM monitors oxygen concentration in the exhaust gas which has passed the warm up three way catalytic converter by HO2S-2. When the catalyst is functioning properly, the variation cycle of HO2S-2 output voltage (oxygen concentration) is slower than that of A/F sensor output signal because of the amount of oxygen in the exhaust gas which has been stored in warm up three way catalytic converter.
A/F Sensor Description
Refer to A/F Sensor Description:For Petrol Engine Model.
DTC Detecting Condition and Trouble Area
Ratio of integrated value of HO2S-2 output variation per integrated value of A/F sensor output variation is more than specification while vehicle is running constant speed and low engine load after warmed up.
(*2 driving cycle detection logic, monitoring once / 1 driving)
DTC detecting condition Trouble area
•Exhaust gas leak
•Warm up three way catalytic converter malfunction
•HO2S-2 malfunction
•A/F sensor malfunction
DTC Confirmation Procedure
WARNING:
•When performing a road test, select a place where there is no traffic or possibility of a traffic accident and be very careful during testing to avoid occurrence of an accident.
•Road test should be carried out by 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that following conditions are satisfied when using this “DTC Confirmation Procedure”.
•Intake air temperature at engine start: –10 °C (14 °F) to 80 °C (176 °F)
•Intake air temperature: –10 °C (14 °F) to 70 °C (158 °F)
•Engine coolant temperature: 70 °C (158 °F) to 150 °C (302 °F)
•Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
1)Connect scan tool to DLC with ignition switch turned OFF.
2)Turn ON ignition switch and clear DTC using scan tool.
3)Increase vehicle speed to 50 – 60 mph, 80 – 100 km/h. (engine speed: 2500 – 3000 r/min.)
4)Keep above vehicle speed for 10 min. or more (Throttle valve opening is kept constant in this step).
5)Stop vehicle and check if DTC / pending DTC exists using scan tool. If not, check if catalyst monitoring test has been completed using scan tool. If not in both of above checks (i.e., no DTC / pending DTC and catalyst monitoring test not completed), check vehicle condition (environmental) and repeat Step 3) through 5).
DTC Troubleshooting
NOTE:
Before this trouble shooting is performed, read the precautions for DTC troubleshooting referring to Precautions for DTC Troubleshooting:For Petrol Engine Model.
алгоритм устранения (там интересен шаг 3):
Мерить выходное напряжение второй лямбды так (думаю можно осциллографом):
HO2S-2 and its circuit check
1)Connect scan tool to DLC with ignition switch turned OFF.
2)Warm up engine to normal operating temperature and keep it at 2000 r/min. for 60 sec.
3)Repeat racing engine (Repeat depressing accelerator pedal 5 to 6 times continuously to enrich A/F mixture and take foot off from pedal to enlean it).
Does HO2S-2 output voltage indicate deflection between over 0.45 V and below 0.25 V?