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 neutral).
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)
- APP SENSOR
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 for the fuel and ignition system circuit connectors for poor connections or loose terminals.
9. Turn the ignition switch to LOCK (0).
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 to LOCK (0).
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)
- APP SENSOR
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 an ignition coil connector(s) (no misfire at this time). Check for poor connections or loose terminals at the ignition coils.
16. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the ignition coil was exchanged?
YES - Replace the faulty ignition coil, Service and Repair then go to step 62.
NO - Go to step 17.
17. Turn the ignition switch to LOCK (0).
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 exchanged?
YES - Replace the faulty spark plug, then go to step 63.
NO - Go to step 22.
22. Turn the ignition switch to LOCK (0).
23. Exchange the injector from the problem cylinder with one from another cylinder.
24. Start the engine, and let it idle for 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 at an injector connector (no misfire at this time). Check for poor connections or loose terminals at the injectors.
27. 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 62.
NO - Go to step 28.
28. Turn the ignition switch to LOCK (0).
29. Disconnect the ignition coil 3P connector from the problem cylinder.
30. Turn the ignition switch to ON (II).
31. Measure the 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 62.
32. Turn the ignition switch to LOCK (0).
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 62.
34. Turn the ignition switch to LOCK (0).
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 of the problem cylinder (see table).
Is there continuity?
YES - Repair short in the wire between the ECM and the ignition coil, then go to step 62.
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 of the problem cylinder (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 62.
40. Reconnect the ignition coil 3P connector and ECM connector A (31P).
41. Do an engine compression and a cylinder leakdown test. Testing and Inspection
Did the engine pass both tests?
YES - Go to step 42.
NO - Repair the engine, then go to step 62.
42. Do the VTEC rocker arm test. VTEC Rocker Arm Test
Did the VTEC rocker arm pass the test?
YES - Go to step 71.
NO - Repair as needed, then go to step 63.
43. Turn the ignition switch to LOCK (0).
44. Jump the SCS line with the HDS.
45. Disconnect ECM connector B (24P).
46. Turn the ignition switch to ON (II).
47. Measure the voltage between body ground and the appropriate ECM connector terminal of the problem cylinder (see table).
Is there battery voltage?
YES - Go to step 56.
NO - Go to step 48.
48. Turn the ignition switch to LOCK (0).
49. Disconnect the injector 2P connector from the problem cylinder.
50. Turn the ignition switch to ON (II).
51. Measure the voltage between injector 2P connector terminal No. 1 and body ground.
It there battery voltage?
YES - Go to step 52.
NO - Repair open in the wire between the injector and PGM-FI main relay 1 (FI MAIN), then go to step 62.
52. Turn the ignition switch to LOCK (0).
53. Check for continuity between body ground and the appropriate ECM connector terminal of the problem cylinder (see table).
Is there continuity?
YES - Repair short in the wire between the ECM and the injector, then go to step 62.
NO - Go to step 54.
54. Connect appropriate injector 2P connector terminal No. 2 to body ground with a jumper wire (see table).
55. Check for continuity between body ground and the appropriate ECM connector terminal of the problem cylinder (see table).
Is there continuity?
YES - Go to step 56.
NO - Repair open in the wire between the ECM and the injector, then go to step 62.
56. 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 57.
NO - Replace the injector, Service and Repair then go to step 62.
57. Install a known-good injector into the problem cylinder.
58. Reconnect all connectors.
59. Start the engine, and let it idle for 2 minutes.
60. 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
61. 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 71.
NO - Replace the original injector, Service and Repair then go to step 62.
62. Reconnect all connectors.
63. Turn the ignition switch to ON (II).
64. Reset the ECM with the HDS.
65. Clear the CKP pattern with the HDS.
66. Do the ECM idle learn procedure. ECM Idle Learn Procedure
67. Do the CKP pattern learn procedure. Initial Inspection and Diagnostic Overview
68. 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
69. 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(s), the injector(s), and the ECM, then go to the DTC P0300, P0301, P0302, P0303, or P0304 troubleshooting. P0300
NO - Go to step 70.
70. 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 69, go to the indicated DTC's 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 68.
71. Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM. Initial Inspection and Diagnostic Overview
72. 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
73. 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(s), the ignition coil(s), and the ECM. If the ECM was updated, substitute a known-good ECM, Initial Inspection and Diagnostic Overview then go to step 71. If the ECM was substituted, go to step 1.
NO - Go to step 74.
74. 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. Service and Repair If any other Temporary DTCs or DTCs were indicated in step 73, go to the indicated DTC's 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, Initial Inspection and Diagnostic Overview 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 72.