Honda Civic. Manual — part 355

1. Turn the ignition switch 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)

A/T in D position (M/T in 5th gear)

Vehicle speed between 45-75 mph (72-120 km/h) for 5 minutes or more
with cruise control set

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 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.

6. Continue the test-drive until a result comes on.
7. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the

troubleshooting information (see 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 H02S (Sensor 2) P0141:
Secondary H02S (Sensor 2) heater

Poor quality fuel may cause this DTC.

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Catalytic Converter System (R18A1) - Civic (Except Hybrid)

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 OFF.
9. Replace the TWC (see CATALYTIC CONVERTER

REMOVAL/INSTALLATION ).

10. Turn the ignition switch ON (II).
11. Reset the ECM/PCM with the HDS.
12. Do the ECM/PCM idle learn procedure (see ECM/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, varying the vehicle speed.
15. Check the CATA MONITOR CONDITION in the DATA LIST with the HDS.

Is the temperature 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)

A/T in D position (M/T in 5th gear)

Vehicle speed at 55 mph (88 km/h) for 5 minutes or more with cruise
control set

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

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Catalytic Converter System (R18A1) - Civic (Except Hybrid)

HDS.

Does the screen indicate EXECUTING?

YES -Go to step 18.

NO -Go to step 16 and recheck.

18. Continue the test-drive until a result comes on.
19. Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?

YES -go to the indicated .

NO -Go to step 20.

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

HDS.

Does the screen indicate PASSED?

YES -Troubleshooting is complete.

NO -If the screen indicates FAILED, check the fuel quality. If the screen
indicates EXECUTING, keep driving until a result comes on. If the screen
indicates OUT OF CONDITION, go to step 13 and recheck.

CATALYTIC CONVERTER REMOVAL/INSTALLATION

1. Remove the A/F sensor (sensor 1) (see A/F SENSOR REPLACEMENT ).
2. Remove the secondary H02S (sensor 2) (see A/F SENSOR

REPLACEMENT ).

3. Remove the EGR pipe (see EGR VALVE REPLACEMENT ).
4. Remove the cover (A).

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Catalytic Converter System (R18A1) - Civic (Except Hybrid)

Fig. 2: Identifying Catalytic Converter Components (With Torque
Specifications)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

5. Remove the TWC (B).
6. Remove the converter cover (C).
7. Install the parts in the reverse order of removal with new gaskets (D).

2008 Honda Civic GX

2006-08 ENGINE PERFORMANCE Catalytic Converter System (R18A1) - Civic (Except Hybrid)