Honda Civic. Manual — part 448

A/T in D position (M/T in 4th gear)

Vehicle speed at 25 mph (40 km/h) for 5 minutes or more

Maintain the vehicle speed at 32 mph (50 km/h) for 5 minutes or more
with cruise control set

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

Is DTC P0400 indicated?

YES - Check for poor connections or loose terminals at the EGR valve and the
ECM/PCM, then go to step 1.

NO - Go to step 12.

12. Monitor the OBD STATUS for DTC P0400 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 11, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose
terminals at the EGR valve and the ECM/PCM, then go to step 1. If the screen
indicates NOT COMPLETED, go to step 10.

DTC P0401: EGR INSUFFICIENT FLOW

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.

NOTE:

Before you troubleshoot, record all freeze data and any on-
board snapshot, and review the general troubleshooting
information (see GENERAL TROUBLESHOOTING
INFORMATION ).

2008 Honda Civic EX

2006-08 ENGINE PERFORMANCE EGR System (R18A1) - Civic (All Except Hybrid)

4. Do the EGR TEST in the INSPECTION MENU with the HDS.

Is the result OK?

YES - Go to step 5.

NO - Go to step 7.

5. Test-drive under these conditions:

Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)

A/T in D position (M/T in 4th gear)

Drive at a steady speed between 55-75 mph (88-120 km/h) for at least 10
seconds

During the drive, decelerate (with the throttle fully closed) for 5 seconds

6. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the

HDS.

Does the screen indicate FAILED?

YES - Clean the intake manifold EGR port and EGR pipe (see EGR VALVE
REPLACEMENT ) with throttle plate and induction cleaner. Also, clean the
passage inside the EGR valve with throttle plate and induction cleaner, then go
to step 9.

NO - If the screen indicates PASSED, intermittent failure, the system is OK at
this time. Check for poor connections or loose terminals at the EGR valve and
the ECM/PCM. If the screen indicates EXECUTING, keep driving until a
result comes on. If the screen indicates OUT OF CONDITION, go to step 5
and recheck.

7. Turn the ignition switch OFF.
8. Replace the EGR valve (see EGR VALVE REPLACEMENT ).
9. Turn the ignition switch ON (II).

10. Reset the ECM/PCM with the HDS.
11. Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN

2008 Honda Civic EX

2006-08 ENGINE PERFORMANCE EGR System (R18A1) - Civic (All Except Hybrid)

PROCEDURE ).

12. Test-drive under these conditions:

Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)

A/T in D position (M/T in 4th gear)

Drive at a steady speed between 55-75 mph (88-120 km/h) for at least 10
seconds

During the drive, decelerate (with the throttle fully closed) for 5 seconds

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

Is DTC P0401 indicated?

YES - Check for poor connections or loose terminals at the EGR valve and the
ECM/PCM. If the connections are OK, go to step 15.

NO - Go to step 14.

14. Monitor the OBD STATUS for DTC P0401 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 13, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose
terminals at the EGR valve and the ECM/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 12.

15. Update the ECM/PCM if it does not have the latest software (see UPDATING

ECM/PCM ), or substitute a known-good ECM/PCM (see SUBSTITUTING
THE ECM/PCM ).

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 4th gear)

2008 Honda Civic EX

2006-08 ENGINE PERFORMANCE EGR System (R18A1) - Civic (All Except Hybrid)

Drive at a steady speed between 55-75 mph (88-120 km/h) for at least 10
seconds

During the drive, decelerate (with the throttle fully closed) for 5 seconds

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

Is DTC P0401 indicated?

YES - Check for poor connections or loose terminals at the EGR valve and the
ECM/PCM. If the ECM/PCM was updated, substitute a known-good
ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step 16. If
the ECM/PCM was substituted, go to step 1.

NO - Go to step 18.

18. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the

HDS.

Does the screen indicate PASSED?

YES - If the ECM/PCM was updated, troubleshooting is complete. If the
ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM
REPLACEMENT ). If any other Temporary DTCs or DTCs were indicated in
step 17, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose
terminals at the EGR valve and the ECM/PCM. If the ECM/PCM was updated,
substitute a known-good ECM/PCM (see SUBSTITUTING THE
ECM/PCM ), then go to step 16. If the ECM/PCM was substituted, 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.

DTC P0404: EGR VALVE CIRCUIT RANGE/PERFORMANCE PROBLEM

NOTE:

Before you troubleshoot, record all freeze data and any on-
board snapshot, and review the general troubleshooting
information (see GENERAL TROUBLESHOOTING
INFORMATION ).

2008 Honda Civic EX

2006-08 ENGINE PERFORMANCE EGR System (R18A1) - Civic (All Except Hybrid)