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 HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, go to step 5. If the HDS indicates EXECUTING, keep idling 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
- 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 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 P0301 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 poor connections or loose terminals in the fuel system circuit.�
9. Turn the ignition switch to LOCK (0).
10. Exchange the ignition coil from the problem cylinder with one 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
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). Check for poor connections or loose terminals at the ignition coil.�
13. 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 40.
NO -
Go to step 14.
14. Turn the ignition switch to LOCK (0).
15. Exchange the spark plug from the problem cylinder with one 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
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 plug was exchanged?
YES -
Replace the faulty spark plug, then go to step 40.
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
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 at 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 40.
NO -
Go to step 25.
25. Do an engine compression and a cylinder leakdown test. Compression Check
Did the engine pass both tests?
YES -
Go to step 26.
NO -
Repair the engine, then go to step 40.
26. Do the VTEC rocker arm test. Rocker Arm Assembly
Did the engine pass the test?
YES -
Go to step 27.
NO -
Repair the VTEC rocker arm, Rocker Arm Assembly then go to step 40.
27. Turn the ignition switch to LOCK (0).
28. Jump the SCS line with the HDS.
29. Disconnect PCM connector C (49P).
30. Turn the ignition switch to ON (II).
31. 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 39.
NO -
Go to step 32.
32. Turn the ignition switch to LOCK (0).
33. Disconnect the injector 2P connector from the problem cylinder.
34. Turn the ignition switch to ON (II).
35. Measure the voltage between injector 2P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to step 36.
NO -
Repair an open in the wire between the injector and PGM-FI main relay 1, then go to step 40.
36. Turn the ignition switch to LOCK (0).
37. Check for continuity between body ground and the 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 40.
NO -
Go to step 38.
38. Check for continuity between appropriate injector 2P connector terminal No. 2 and the PCM connector terminal of the problem cylinder (see table).
Is there continuity?
YES -
Go to step 39.
NO -
Repair an open in the wire between the PCM and the injector, then go to step 40.
39. 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 50.
NO -
Replace the injector Service and Repair, then go to step 40.
40. Turn the ignition switch to LOCK (0).
41. Reconnect all connectors.
42. Turn the ignition switch to ON (II).
43. Reset the PCM with the HDS.
44. Do the CKP pattern clear procedure. Initial Inspection and Diagnostic Overview
45. Do the PCM idle learn procedure. PCM Idle Learn Procedure
46. Do the CKP pattern learn procedure. Initial Inspection and Diagnostic Overview
47. 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
48. 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 the troubleshooting for DTC P0300, P0301, P0302, P0303, or P0304 P0300.
NO -
Go to step 49.
49. 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 48 P0301, go to the indicated DTC's troubleshooting.�
NO -
If the HDS 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 HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION or NOT COMPLETED, go to step 47.
50. Reconnect all connectors.
51. Update the PCM if it does not have the latest software, PCM Update or substitute a known-good PCM. Initial Inspection and Diagnostic Overview
52. 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
53. 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 52. If the PCM was substituted, go to step 1.
NO -
Go to step 54.
54. 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 53 P0301, go to the indicated DTC's troubleshooting.�
NO -
If the HDS 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, then go to step 52. 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 52.