DTC Troubleshooting
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: Secondary HO2S (Sensor 2)
P0141, P0161: Secondary HO2S (Sensor 2) heater
- 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 with cruise control set
- Vehicle speed between 55-75 mph (88-120 km/h) for 10 seconds, then decelerate (with throttle fully closed). Repeat this 3 times or more
- 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 screen indicate EXECUTING?
YES - Go to step 6.
NO - If the screen indicates OUT OF CONDITION, go to step 4 and recheck. If the screen indicates PASSED, intermittent failure, the system is OK at this time. If the screen indicates FAILED, go to step 8 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, the system is OK at this time. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen 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 ON mode.
9. Replace the WU-TWC:
- For DTC P0420, replace the rear WU-TWC (Bank 1). Warm Up TWC Removal/Installation
- For DTC P0430, replace the front WU-TWC (Bank 2). Warm Up TWC Removal/Installation
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 throttle fully closed). Repeat this 3 times or more
- 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 the 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 screen 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 screen indicates FAILED, check the fuel quality, then go to step 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 15.