DTC Troubleshooting
DTC Troubleshooting: P0301 (71), P0302 (72), P0303 (73), P0304 (74)
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 HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, go to step 5. If the HDS indicates EXECUTING, let the engine idle until a result comes on. If the HDS indicates OUT OF CONDITION or NOT COMPLETED, 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
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
7. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, go to step 8. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION or NOT COMPLETED, 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 for loose wires or poor connections in the fuel system circuit.
9. Turn the ignition switch to LOCK (0).
10. Remove the charge air cooler, and the injector cover, then reinstall the charge air cooler.
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 22.
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
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
15. 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 16.
NO -
Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time). Check for poor connections or loose terminals at the ignition coil.
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 56.
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
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
20. 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 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 56.
NO -
Go to step 22.
22. Turn the ignition switch to LOCK (0).
23. Exchange the injector from the problem cylinder with one from the 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
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
26. 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 27.
NO -
Intermittent misfire due to poor contact at 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 exchanged?
YES -
Replace the faulty injector Service and Repair, then go to step 56.
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 an open in the wire between the ignition coil and the ignition coil relay, then go to step 56.
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 an open in the wire between the ignition coil and G101, then go to step 56.
34. Jump the SCS line with the HDS.
35. Disconnect PCM connector C (44P).
36. Check for continuity between body ground and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Repair a short in the wire between the PCM and the ignition coil, then go to step 56.
NO -
Go to step 37.
37. Check for continuity between appropriate ignition coil 3P connector terminal No. 1 and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Go to step 38.
NO -
Repair an open in the wire between the PCM and the ignition coil, then go to step 56.
38. Reconnect all connectors.
39. Do an engine compression and a cylinder leak-down test Testing and Inspection.
Did the engine pass both tests?
YES -
Go to step 40.
NO -
Repair the engine, then go to step 56.
40. Do the VTEC rocker arm test VTEC Rocker Arm Test.
Did the engine pass the test?
YES -
Go to step 41.
NO -
Replace the VTEC rocker arm Rocker Arm Assembly Removal, then go to step 56.
41. Turn the ignition switch to LOCK (0).
42. Disconnect the injector 2P connector from the problem cylinder.
43. Turn the ignition switch to ON (II).
44. Measure the voltage between injector 2P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to step 45.
NO -
Repair an open in the wire between the injector and PGM-FI main relay 1, then go to step 56.
45. Turn the ignition switch to LOCK (0).
46. Jump the SCS line with the HDS.
47. Disconnect PCM connector C (44P).
48. Check for continuity between body ground and the appropriate PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Repair a short in the wire between the PCM and the injector, then go to step 56.
NO -
Go to step 49.
49. Check for continuity between the appropriate PCM connector terminal of the problem cylinder and appropriate injector 2P connector terminal No. 2 (see table).
Is there continuity?
YES -
Go to step 50.
NO -
Repair an open in the wire between the PCM and the injector, then go to step 56.
50. 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 51.
NO -
Replace the injector Service and Repair, then go to step 57.
51. Substitute a known-good injector into the problem cylinder.
52. Reconnect all connectors.
53. Start the engine, and let it idle for 2 minutes.
54. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
55. 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 65.
NO -
Replace the original injector Service and Repair, then go to step 56.
56. Turn the ignition switch to LOCK (0).
57. Reconnect all connectors.
58. Turn the ignition switch to ON (II).
59. Reset the PCM with the HDS.
60. Do the PCM idle learn procedure PCM Idle Learn Procedure.
61. Do the CKP pattern clear/CKP pattern learn procedure.
62. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
63. 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, then go to step 62. If the PCM was substituted, go to step 1.
NO -
Go to step 64.
64. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS indicate PASSED?
YES -
Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 63, go to the indicated DTC's troubleshooting.
NO -
If the HDS indicates FAILED, check for poor connections or loose terminals at the ignition coil, the injector, and the PCM, then go to step 1. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION or NOT COMPLETED, go to step 62.
65. Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM.
66. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- VEHICLE SPEED
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
- GEAR POSITION
67. 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 coil, the injector, and the PCM. If the PCM was updated, substitute a known-good PCM, then go to step 66. If the PCM was substituted, go to step 1.
NO -
Go to step 68.
68. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS 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 67, go to the indicated DTC's troubleshooting.
NO -
If the HDS indicates FAILED, check for poor connections or loose terminals at the ignition coil, the injector, and the PCM. If the PCM was updated, substitute a known-good PCM, then go to step 66. If the PCM was substituted, go to step 1. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION or NOT COMPLETED, go to step 66.