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, P2270, P2271, P2272*, P2273*: Secondary HO2S (Sensor 2)
P0141, P0161: Secondary HO2S (Sensor 2) heater
- P0300: Random misfire.
- 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).
2. Clear the DTC with the HDS.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) 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 position
- Vehicle speed between 45-75 mph (72-120 km/h) for 5 minutes or more
- Maintain the vehicle speed at 55 mph (88 km/h) for 1 minute 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 - 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, 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).
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).
11. Reset the PCM with the HDS.
12. Do the PCM idle learn procedure. PCM Idle Learn Procedure
13. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle.
14. Test-drive for about 10 minutes, continually changing the vehicle speed.
15. Check the CATA MONITOR CONDITION B1 (B2)* in the DATA LIST with the HDS.
Is the condition OK?
YES - Go to step 16.
NO - Go to step 13 and recheck.
16. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D position
- Vehicle speed between 45-75 mph (72-120 km/h) for 5 minutes or more
- Maintain the vehicle speed at 55 mph (88 km/h) for 1 minute or more with cruise control set.
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.
Is DTC P0420 and/or P0430* indicated?
YES - Check for poor connections or loose terminals at the secondary HO2S (sensor 2) and the PCM, then go to step 1.
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. If any other Temporary DTCs or DTCs were indicated in step 19, go to the indicated DTC's troubleshooting.
NO - If the screen indicates FAILED, check for poor connections or loose terminals at the secondary HO2S (Sensor 2) and the PCM, 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 16.