P0420

DTC P0420 / P0430: Catalyst System Efficiency Below Threshold (Bank-1 / -2)

System / Wiring Diagram:

System / Wiring Diagram

System Description
ECM monitors oxygen concentration in the exhaust gas which has passed the warm up three way catalytic converter by HO2S. When the catalyst is functioning properly, the variation cycle of HO2S output voltage (oxygen concentration) is slower than that of A/F sensor output signal because the amount of oxygen in the exhaust gas is stored in warm up three way catalytic converter.

A/F Sensor Description
Refer to A/F Sensor Description.

DTC Detecting Condition And Trouble Area:

DTC Detecting Condition and Trouble Area

DTC Confirmation Procedure

WARNING:
- When performing a road test, select a place where there is no traffic or possibility of a traffic accident and very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and a tester, on a level road.

NOTE:
Check to make sure that the following conditions are satisfied when using this "DTC Confirmation Procedure".
- Intake air temperature: between -14 °C and 70 °C (6.8 °F and 158 °F).
- Engine coolant temperature: higher than 58 °C (136 °F).
- The following DTCs are not detected: A/F sensor, A/F sensor heater, HO2S-2 and HO2S-2 heater.

1. With ignition switch OFF, connect scan tool.
2. Turn ON ignition switch and clear DTC by using scan tool if any.
3. Start engine and warm up to normal operating temperature.
4. Increase vehicle speed to 35 mph (56 km/h) or more.
5. Keep above vehicle speed for 5 min. (Throttle valve operating is kept constant in this step.)
6. Increase vehicle speed to 50 - 60 mph (80 - 100 km/h). (engine speed; 2500 - 3000 rpm)
7. Keep above vehicle speed for 5 min. (Throttle valve operating is kept constant in this step.)
8. Stop vehicle and check DTC and pending DTC by using scan tool.

Step 1-4:

DTC Troubleshooting