( TL19E3HK72100090420FAAT00 )

DTC Troubleshooting: P0420 (67)

DTC P0420:
Catalyst System Efficiency Below Threshold
NOTE:

- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
- If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot them first, then recheck for DTC P0420.
  P0137, P0138: Secondary HO2S (Sensor 2)
  P0141: Secondary HO2S (Sensor 2) heater
- P0300: Random misfire
  P0301−P0304: No. 1, No. 2, No. 3, or No. 4 cylinder misfire detected
- Poor quality fuel may cause this DTC.

1. Turn the ignition switch to ON (II).

1. Clear the DTC with the HDS.

1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.

1. Test-drive under these conditions:
   - Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
   - A/T in D, M/T in 4th or 5th
   - Vehicle speed between 72−120 km/h (45−75 mph) for 5 minutes or more with cruise control set
   - Vehicle speed between 88−120 km/h (55−75 mph) for 10 seconds, then decelerate (with throttle fully closed). Repeat this 3 times or more
   - Maintain the vehicle speed at 88 km/h (55 mph) for 5 minutes or more with cruise control set

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

Does the screen indicate FAILED?

YES | - | Go to Step 6 .
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 or NOT COMPLETED, go to Step 4 and recheck.

1. Turn the ignition switch to LOCK (0).

1. Replace the WU-TWC.

1. Turn the ignition switch to ON (II).

1. Reset the ECM/PCM with the HDS.

1. Do the ECM/PCM idle learn procedure.

1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.

1. Test-drive for about 10 minutes, varying the vehicle speed.

1. Check the CATA MONITOR CONDITION in the DATA LIST with the HDS.

Is the temperature OK?

YES | - | Go to Step 14 .
NO | - | Go to Step 11 and recheck.

1. Test-drive under these conditions:
   - Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
   - Vehicle speed between 88−120 km/h (55−75 mph) for 10 seconds, then decelerate (with throttle fully closed). Repeat this 3 times or more
   - Maintain the vehicle speed at 88 km/h (55 mph) for 5 minutes or more with cruise control set

1. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0420 indicated?

YES | - | Check the fuel quality, then go to Step 1 .
NO | - | Go to Step 16 .

1. Monitor the OBD STATUS for DTC P0420 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 15 , 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 or NOT COMPLETED, go to Step 11 .