P0420

DTC P0420: Rear Bank Catalyst System Efficiency Below Threshold (Bank 1)

NOTE:
- If some of the DTCs listed below are stored at the same time as DTC P0420 and/or P0430*, troubleshoot those DTCs first, then recheck for DTC P0420 and/or P0430*.
- P0137,P0138, P0157, P0158: Secondary HO2S (Sensor 2) P0141, P0161: Secondary HO2S (Sensor 2) Heater
- When poor quality fuel is used, this DTC may be indicated.
- Information marked with an asterisk (*) applies to the front bank.

1. Turn the ignition switch ON (II).
2. Clear the DTC with the HDS.
3. Start the engine. Hold the engine speed at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
4. Test-drive under the following conditions.
- Engine coolant temperature more than 158 °F (70 °C)
- A/T in D position
- Vehicle speed between 50 mph (80 km/h) and 55 mph (88 km/h) with cruise control
- Drive about 2 minutes, then decelerate for at least 4 seconds with the throttle completely closed, then accelerate to 55 mph (88 km/h) for 20 minutes with cruise control.

5. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the screen indicate EXECUTING?

YES - Go to step 6.

NO - Go to step 4 and recheck.

6. Continue test driving until a result comes on.
7. Monitor the OBD STATUS for DTC P0420 and/or P0430* in the DTCs MENU with the HDS.

Does the screen indicate FAILED?

YES - Go to step 8.

NO - If the screen indicates PASSED, intermittent failure, system is OK at this time. If the screen indicates EXECUTING, keep the driving condition continually until a result comes on. If the screen indicates OUT OF CONDITION, go to step 5 and recheck.

8. Turn the ignition switch OFF.
9. Replace the WU-TWC.
10. Turn the ignition switch ON (II).
11. Reset the PCM with the HDS.
12. Do the PCM idle learn procedure.
13. Start the engine. Hold the engine speed at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
14. Test-drive for about 10 minutes, varying the vehicle speed.
15. Check the CATA MON TEMP in the DATA LIST with the HDS.

Is it OK?

YES - Go to step 16.

NO - Go to step 13 and recheck.

16. Test-drive under the following conditions.
- Engine coolant temperature more than 158 °F (70 °C)
- Transmission in D position
- Vehicle speed between 50 mph (80 km/h) and 55 mph (88 km/h) with cruise control
- Drive about 2 minutes, then decelerate for at least 4 seconds with the throttle completely closed, then accelerate to 55 mph (88 km/h) for 20 minutes with cruise control

17. Monitor the OBD STATUS for DTC P0420 and/or P0430* in the DTCs MENU with the HDS.

Does the screen indicate EXECUTING?

YES - Go to step 18.

NO - Go to step 16 and recheck.

18. Continue test driving until a result comes on.
19. Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?

YES - Go to the indicated DTC's troubleshooting.

NO - Go to step 20.

20. Monitor the OBD STATUS for DTC P0420 and/or P0430* in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES - Troubleshooting is complete.

NO - If the screen indicates FAILED, check the fuel quality. If the screen indicates EXECUTING, keep the driving condition continually until a result comes on. If the screen indicates OUT OF CONDITION, go to step 13 and recheck.