Honda Accord 2008 Manual page 710

07/11/02 09:19:14 61TA0000_110_0391
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 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).
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 °F (70 °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
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
10. Do the ECM/PCM idle learn procedure (see page
11. Start the engine. Hold the engine speed at
− − 12. Test-drive for about 10 minutes, varying the vehicle
− −
13. Check the CATA MONITOR CONDITION in the
ＴＡ０８ＡＥＡＫ７２１０００９０４２０ＦＡＡＴ３０
5. Monitor the OBD STATUS for DTC P0420 in the
DTCs MENU with the HDS.
Does the screen indicate F AILED?
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.
6. Turn the ignition switch to LOCK (0).
7. Replace the WU-TWC (see page 11-393).
8. Turn the ignition switch to ON (II).
9. Reset the ECM/PCM with the HDS.
11-343).
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.
speed.
DATA LIST with the HDS.
Is the temperature OK ?
−
YES Go to step 14.
NO − Go to step 11 and recheck.
(cont'd)
11-391