Honda Accord: DTC Troubleshooting
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 (see page 11-3).
- 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 H02S (Sensor 2)
P0141: Secondary H02S (Sensor 2) heater
-СћP0300: 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).
2. Clear the DTC with the HDS.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in 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 Р’В°F (70 Р’В°C)
- 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 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 in the DTCs MENU with the HDS.
Does the screen indicate FAILED? YES
-Go to step 6.
NO
-lf 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.
6. Turn the ignition switch to LOCK (0).
7. Replace the WU-TWC (see page 11-339).
8. Turn the ignition switch to ON (II).
9. Reset the ECM/PCM with the HDS.
10. Do the ECM/PCM idle learn procedure (see page 11-293).
11. Test-drive for about 10 minutes, varying the vehicle speed.
12. Check the CATA MONITOR CONDITION in the DATA LIST with the HDS.
Is the condition OK? YES-Go to step 13.
NO-Go to step 11 and recheck.
13. Test-drive under these conditions: - Engine coolant temperature (ECT SENSOR 1) above 158 В°F (70 В°C) - 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
14. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0420 indicated? YES
-Check the fuel quality, then go to step 1.
NO
-Go to step 15.
15. 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 Pending or Confirmed DTCs were indicated in step 14, go to the indicated DTCs troubleshooting.- NO
-lf 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 13.
Warm Up TWC Removal/Installation
1. Raise the vehicle on a lift.
2. Remove the secondary H02S (Sensor 2) (see page
11-197).
3. Remove the bolts (A).
4. Remove the WU-TWC bracket (B).
5. Lower the vehicle.
6. Remove th ...
See also:
System Description
Security Alarm
The security alarm system is armed automatically after
the doors, hood, and trunk lid are closed and locked. For
the system to arm, the ignition switch must be in the
LOCK (0) posit ...
To Turn Everything Off
To turn the system completely off,
press the ON/OFF button.
Keep the system completely off
for short periods only.
To keep stale air and mustiness
from collecting, you should have
the fan ru ...