P0420

DTC Troubleshooting: P0420, P0430

DTC P0420:

Rear Bank Catalyst System Efficiency Below Threshold (Bank 1)

DTC P0430:

Front Bank Catalyst System Efficiency Below Threshold (Bank 2)

NOTE:

- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information Initial Inspection and Diagnostic Overview.
- 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*, P2270, P2272*: Secondary HO2S (Sensor 2)
P0141, P0161*: Secondary HO2S (Sensor 2) heater
P0300: Random misfire detected
P0301-P0306: No. 1, No. 2, No. 3, No. 4, No. 5, or No. 6 cylinder misfire detected
- Poor quality fuel can cause these DTCs.
- Information marked with an asterisk (*) applies to the front bank (Bank 2).

1. Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

2. Clear the DTC with the HDS.

3. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.

4. Test-drive under these conditions:

- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- Vehicle speed between 45-75 mph (72-120 km/h) for 5 minutes or more
- Vehicle speed between 55-75 mph (88-120 km/h) for 10 seconds, then decelerate (with the throttle fully closed). Repeat this three or more times.
- Maintain the vehicle speed at 55 mph (88 km/h) for 5 minutes or more with cruise control set

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

Does the HDS indicate EXECUTING?

YES -

Go to step 6.

NO -

If the HDS indicates OUT OF CONDITION, go to step 4 and recheck. If the HDS indicates PASSED, intermittent failure, the system is OK at this time. If the HDS indicates FAILED, go to step 8.

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 HDS indicate FAILED?

YES -

Go to step 8.

NO -

If the HDS indicates PASSED, intermittent failure, the system is OK at this time. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 4 and recheck.

8. Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

9. Replace the WU-TWC:

- For DTC P0420, replace the rear WU-TWC (Bank 1).
- For DTC P0430, replace the front WU-TWC (Bank 2).

10. Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

11. Reset the PCM with the HDS.

12. Do the PCM idle learn procedure PCM Idle Learn Procedure.

13. Test-drive for about 10 minutes, continually changing the vehicle speed.

14. Check the CATA MONITOR CONDITION B1 (B2)* in the DATA LIST with the HDS.

Is the condition OK?

YES -

Go to step 15.

NO -

Go to step 13 and recheck.

15. Test-drive under these conditions:

- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- Vehicle speed between 55-75 mph (88-120 km/h) for 10 seconds, then decelerate (with the throttle fully closed). Repeat this three or more times.
- Maintain the vehicle speed at 55 mph (88 km/h) for 5 minutes or more with cruise control set.

16. Continue test driving until a result comes on.

17. Check for Pending or Confirmed DTCs with the HDS.

Is DTC P0420 and/or P0430* indicated?

YES -

Check for fuel quality, then go to step 1.

NO -

Go to step 18.

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

Does the HDS indicate PASSED?

YES -

Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 17, go to the indicated DTC's troubleshooting.�

NO -

If the HDS indicates FAILED, check the fuel quality, then go to step 1. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 15.