DTC Troubleshooting
DTC P0301: No. 1 Cylinder Misfire DetectedDTC 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.
1. Turn the ignition switch OFF.
2. Clear the DTC with the HDS.
3. Start the engine (in neutral), then let it idle without load.
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 indicate 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 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)
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 indicate 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 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 the fuel and ignition system circuit connections for loose wires or poor connections.
9. Turn the ignition switch OFF.
10. Remove the fuel rail cover.
11. Start the engine, and listen for a clicking sound at the injector of the problem cylinder.
Does the injector click?
YES - Go to step 12.
NO - Go to step 43.
12. Turn the ignition switch OFF.
13. Exchange the ignition coil from the problem cylinder with one from another cylinder.
14. 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)
15. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE show misfire counts?
YES - Go to step 16.
NO - Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time). Make sure the coil connections are secure.
16. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the ignition coil was moved?
YES - Replace the faulty ignition coil, then Go to step 63.
NO - Go to step 17.
17. Turn the ignition switch OFF.
18. Exchange the spark plug from the problem cylinder with one from another cylinder.
19. 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)
20. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE show misfire counts?
YES - Go to step 21.
NO - Intermittent misfire due to spark plug fouling (no misfire at this time).
21. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the spark plug was moved?
YES - Replace the faulty spark plug, then Go to step 63.
NO - Go to step 22.
22. Turn the ignition switch OFF.
23. Exchange the injector from the problem cylinder with one from the another cylinder.
24. Start the engine, and let it idle 2 minutes.
25. 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)
26. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE show misfire counts?
YES - Go to step 27.
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.
27. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the injector was moved?
YES - Replace the faulty injector, then Go to step 63.
NO - Go to step 28.
28. Turn the ignition switch OFF.
29. Disconnect the ignition coil 3P connector from the problem cylinder.
30. Turn the ignition switch ON (II).
31. Measure voltage between ignition coil 3P connector terminal No. 3 and body ground.
Is there battery voltage?
YES - Go to step 32.
NO - Repair open in the wire between the ignition coil and the ignition coil relay, then Go to step 63.
32. Turn the ignition switch OFF.
33. Check for continuity between ignition coil 3P connector terminal No. 2 and body ground.
Is there continuity?
YES - Go to step 34.
NO - Repair open in the wire between the ignition coil and G101, then Go to step 63.
34. Turn the ignition switch OFF.
35. Jump the SCS line with the HDS.
36. Disconnect ECM connector A (31P).
37. Check for continuity between body ground and the appropriate ECM connector terminal (see table).
Is there continuity?
YES - Repair short in the wire between the ECM and the ignition coil, then Go to step 63.
NO - Go to step 38.
38. Connect appropriate ignition coil 3P connector terminal No. 1 to body ground with a jumper wire (see table).
39. Check for continuity between body ground and the appropriate ECM connector terminal (see table).
Is there continuity?
YES - Go to step 40.
NO - Repair open in the wire between the ECM and the ignition coil, then Go to step 63.
40. Reconnect the ignition coil 3P connector and ECM connector A (31P).
41. Do an engine compression and a cylinder leak down test.
Did the engine pass both tests?
YES - Go to step 42.
NO - Repair the engine, then Go to step 63.
42. Do the VTEC rocker arm test.
Did the VTEC rocker arm pass the test?
YES - Go to step 72.
NO - Repair as necessary, then Go to step 63.
43. Turn the ignition switch OFF.
44. Jump the SCS line with the HDS.
45. Disconnect ECM connector B (24P).
46. Turn the ignition switch ON (II).
47. Measure voltage between body ground and the appropriate ECM connector terminal (see table).
Is there battery voltage?
YES - Go to step 57.
NO - Go to step 48.
48. Turn the ignition switch OFF.
49. Remove the fuel rail cover.
50. Disconnect the injector 2P connector from the problem cylinder.
51. Turn the ignition switch ON (II).
52. Measure voltage between injector 2P connector terminal No. 1 and body ground.
It there battery voltage?
YES - Go to step 53.
NO - Repair open in the wire between the injector and PGM-FI main relay 1 (FI MAIN), then Go to step 63.
53. Turn the ignition switch OFF.
54. Check for continuity between body ground and the appropriate ECM connector terminal (see table).
Is there continuity?
YES - Repair short in the wire between the ECM and the injector, then Go to step 63.
NO - Go to step 55.
55. Connect appropriate injector 2P connector terminal No, 2 to body ground with a jumper wire (see table).
56. Check for continuity between body ground and the appropriate ECM connector terminal (see table).
Is there continuity?
YES - Go to step 57.
NO - Repair open in the wire between the ECM and the injector, then Go to step 63.
57. At the injector side, measure resistance between injector 2P connector terminals No. 1 and No. 2.
Is there 10-13 ohms ?
YES - Go to step 58.
NO - Replace the injector, then Go to step 63.
58. Exchange a known-good injector from another cylinder with the one from the problem cylinder.
59. Reconnect ECM connector B (24P).
60. Start the engine, and let it idle for 2 minutes.
61. 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)
62. Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE show misfire counts?
YES - Go to step 72.
NO - Replace the original injector, then Go to step 63.
63. Reconnect all connectors.
64. Turn the ignition switch ON (II).
65. Reset the ECM with the HDS.
66. Clear the CKP pattern with the HDS.
67. Do the ECM idle learn procedure.
68. Do the CKP pattern learn procedure.
69. 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)
70. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0301, P0302, P0303, or P0304 indicated?
YES - Check for poor connections or loose terminals at the ignition coil, the injector, and the ECM, then Go to DTC P0300, P0301, P0302, P0303 or P0304 troubleshooting.
NO - Go to step 70.
71. Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 70, Go to the indicated DTCs troubleshooting.
NO - If the screen indicate FAILED, Go to step 1 and recheck. If the screen indicated EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, Go to step 69.
72. Update the ECM if it does not have the latest software, or substitute a known-good ECM.
73. 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)
74. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0301, P0302, P0303 or P0304 indicated?
YES - Check for poor connections or loose terminals at the injector, the ignition coil, and the ECM.
NO - Go to step 75.
75. 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 ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. If any other Temporary DTCs or DTCs were indicated in step 74, Go to the indicated DTCs troubleshooting.
NO - If the screen indicates FAILED, check for poor connections or loose terminals at the ignition coil, the injector, and the ECM. If the ECM was updated, substitute a known-good ECM, then Go to step 72. If the ECM 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 73.