P0420

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

Wiring Diagram:

System / Wiring Diagram

System Description
Exhaust oxygen concentration at the upper part and the lower part of WU-TWC is detected from HO2S-1 and HO2S-2 respectively and accordingly ECM (PCM) controls the closed loop which then controls the fuel injection volume. While the above control is going on and if WUTWC is in good condition, the output voltage of HO2S-2 is maintained at specified level. As WU-TWC becomes deteriorated, even when the above control is going on, the exhaust gas which has passed WU-TWC then passes HO2S-2 at the exhaust oxygen concentration similar to that of the upper part of WU-TWC without being oxygenated or converted. Thus, waveforms of HO2S-1 and HO2S-2 output voltage become alike. ECM (PCM) judges deterioration of WU-TWC by comparing waveforms of HO2S-1 and HO2S-2.

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)
- Atmospheric pressure: higher than 560 mmHg (Altitude: lower than 2790 m (9150 ft))
- The following DTCs are not detected: P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0141, P0335, P0461, P0463, P0500, P2227, P2228 and P2229

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 56 km/h (35 mph) or more.
5. Keep above vehicle speed for 5 min. (Throttle valve operating is kept constant in this step.)
6. Increase vehicle speed to 80 - 100 km/h (50 - 60 mph). (engine speed; 2500 - 3000 rpm)
7. Keep above vehicle speed for 1 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

NOTE: Parts, exhaust manifold and exhaust pipe No.2 include warm up three way catalytic converter (WU-TWC) and three way catalytic converter (TWC), respectively.