DTC Troubleshooting
DTC Troubleshooting: P0301, P0302, P0303, P0304
DTC P0301:
No. 1 Cylinder Misfire Detected
DTC P0302:
No. 2 Cylinder Misfire Detected
DTC P0303:
No. 3 Cylinder Misfire Detected
DTC P0304:
No. 4 Cylinder Misfire Detected
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information Initial Inspection and Diagnostic Overview.
1. Turn the ignition switch to ON (II).
2. Clear the DTC with the HDS.
3. Start the engine , and let it idle without load (in P or N).
4. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES -
Go to step 9.
NO -
If the screen indicates PASSED, go to step 5. If the screen indicates EXECUTING, keep idling until a result comes on. If the screen indicates OUT OF CONDITION, wait for several minutes, and recheck.
5. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE show misfire counts?
YES -
Go to step 9.
NO -
Go to step 6.
6. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
7. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES -
Go to step 9.
NO -
If the screen indicates PASSED, go to step 8. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 6 and recheck.
8. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE show misfire counts?
YES -
Go to step 9.
NO -
Intermittent failure, the system is OK at this time. Check poor connections or loose terminals in the fuel system and the ignition system.�
9. Turn the ignition switch to LOCK (0).
10. Exchange the ignition coils from the problem cylinder with those from another cylinder.
11. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
12. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE show misfire counts?
YES -
Go to step 13.
NO -
Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time). Make sure that the ignition coil connectors are secure.�
13. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the ignition coils were exchanged?
YES -
Replace the faulty ignition coil Service and Repair, then go to step 49.
NO -
Go to step 14.
14. Turn the ignition switch to LOCK (0).
15. Exchange the spark plugs from the problem cylinder with those from another cylinder.
16. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
17. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE show misfire counts?
YES -
Go to step 18.
NO -
Intermittent misfire due to spark plug fouling (no misfire at this time).�
18. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the spark plugs were exchanged?
YES -
Replace the faulty spark plug, then go to step 49.
NO -
Go to step 19.
19. Turn the ignition switch to LOCK (0).
20. Exchange the injector from the problem cylinder with one from the another cylinder.
21. Start the engine, and let it idle for 2 minutes.
22. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
23. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, and/or CYL4 MISFIRE show misfire counts?
YES -
Go to step 24.
NO -
Intermittent misfire due to bad contact in the injector connector (no misfire at this time). Check for poor connections or loose terminals at the injector.�
24. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the injector was exchanged?
YES -
Replace the faulty injector Service and Repair, then go to step 49.
NO -
Go to step 25.
25. Turn the ignition switch to LOCK (0).
26. Disconnect the ignition coil 3P connectors from the problem cylinder.
27. Turn the ignition switch to ON (II).
28. Measure the voltage between ignition coil 3P connector terminal No. 3 and body ground.
Is there battery voltage?
YES -
Go to step 29.
NO -
Repair open in the wire between the ignition coil and the No. 14 IGNITION COIL (IN) (15 A) fuse (or No. 13 IGNITION COIL (EX) (15 A) fuse)*, then go to step 47.
29. Turn the ignition switch to LOCK (0).
30. Check for continuity between ignition coil 3P connector terminal No. 2 and body ground.
Is there continuity?
YES -
Go to step 31.
NO -
Repair open in the wire between the ignition coil and G102 Connector and Harness Locations, then go to step 47.
31. Jump the SCS line with the HDS.
32. Disconnect PCM connector C (44P).
33. Check for continuity between body ground and the appropriate PCM connector terminal of the problem cylinder (see table).
FRONT (INTAKE) SIDE:
REAR (EXHAUST) SIDE:
Is there continuity?
YES -
Repair short in the wire between the PCM and the ignition coil, then go to step 47.
NO -
Go to step 34.
34. Check for continuity between appropriate ignition coil 3P connector terminal No. 1 and the appropriate PCM connector terminal of the problem cylinder (see table).
FRONT (INTAKE) SIDE:
REAR (EXHAUST) SIDE:
Is there continuity?
YES -
Go to step 35.
NO -
Repair open in the wire between the PCM and the ignition coil, then go to step 47.
35. Do an engine compression and a cylinder leakdown test Testing and Inspection.
Did the engine pass both tests?
YES -
Go to step 36.
NO -
Repair the engine, then go to step 47.
36. Do the VTEC rocker arm test VTEC Rocker Arm Test.
Did the engine pass the test?
YES -
Go to step 37.
NO -
Repair the VTEC rocker arm Rocker Arm and Shaft Disassembly/Reassembly, then go to step 47.
37. Turn the ignition switch to ON (II).
38. Measure the voltage between body ground and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there battery voltage?
YES -
Go to step 46.
NO -
Go to step 39.
39. Turn the ignition switch to LOCK (0).
40. Disconnect the injector 2P connector from the problem cylinder.
41. Turn the ignition switch to ON (II).
42. Measure the voltage between injector 2P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to step 43.
NO -
Repair open in the wire between the injector and PGM-FI main relay 1, then go to step 47.
43. Turn the ignition switch to LOCK (0).
44. Check for continuity between body ground and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Repair short in the wire between the PCM and the injector, then go to step 47.
NO -
Go to step 45.
45. Check for continuity between appropriate injector 2P connector terminal No. 2 and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Go to step 46.
NO -
Repair open in the wire between the PCM and the injector, then go to step 47.
46. At the injector side, measure the resistance between injector 2P connector terminals No. 1 and No. 2.
Is there 10-13 Ohms?
YES -
Go to step 56.
NO -
Replace the injector Service and Repair, then go to step 47.
47. Turn the ignition switch to LOCK (0).
48. Reconnect all connectors.
49. Turn the ignition switch to ON (II).
50. Reset the PCM with the HDS.
51. Do the PCM idle learn procedure PCM Idle Learn Procedure.
52. Do the CKP pattern clear/CKP pattern learn procedure Initial Inspection and Diagnostic Overview.
53. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
54. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0301, P0302, P0303, or P0304 indicated?
YES -
Check for poor connections or loose terminals at the ignition coils, the injectors, and the PCM, then go to troubleshooting DTC P0300, P0301, P0302, P0303, or P0304 P0300.
NO -
Go to step 55.
55. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 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 54, go to the indicated DTC's troubleshooting.�
NO -
If the screen indicates FAILED, check for poor connections or loose terminals at the ignition coils, the injectors, and the 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 53.
56. Reconnect all connectors.
57. Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM Initial Inspection and Diagnostic Overview.
58. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VSS
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- ECT SENSOR 1
59. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0301, P0302, P0303, or P0304 indicated?
YES -
Check for poor connections or loose terminals at the ignition coils, the injectors, and the PCM. If the PCM was updated, substitute a known-good PCM Initial Inspection and Diagnostic Overview, then go to step 58. If the PCM was substituted, go to step 1.
NO -
Go to step 60.
60. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -
If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM Service and Repair. If any other Pending or Confirmed DTCs were indicated in step 59, go to the indicated DTC's troubleshooting.�
NO -
If the screen indicates FAILED, check for poor connections or loose terminals at the ignition coils, the injectors, and the PCM. If the PCM was updated, substitute a known-good PCM Initial Inspection and Diagnostic Overview, then go to step 58. If the 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 58.