## DTC Troubleshooting: P0301 (71-1), P0302 (72-1), P0303 (73-1), P0304 (74-1)

DTC P0301 (71-1): | No. 1 Cylinder Misfire
DTC P0303 (73-1): | No. 3 Cylinder Misfire

1. | After checking and recording the freeze data, reset the ECM/PCM. If there is no freeze data of the misfire, just clear the DTC.

2. | Start the engine, and listen for a clicking sound at the injector at the problem cylinder. Does it click? YES - Go to 3. NO - Go to 24.

3. | Turn the ignition switch OFF, and reset the ECM/PCM.

4. | Exchange the ignition coil from the problem cylinder with one from another cylinder.

5. | Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

6. | Check the DTC or the Temporary DTC with the scan tool. Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated? YES - Go to 7. NO - Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time).n

7. | Determine which cylinder(s) had the misfire. Does the misfire occur in the other cylinder whose ignition coil was exchanged? YES - Replace the faulty ignition coil.n NO - Go to 8.

8. | Turn the ignition switch OFF, and reset the ECM/PCM.

9. | Exchange the spark plug from the problem cylinder with one from another cylinder.

10. | Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

11. | Check the DTC or the Temporary DTC with the scan Tool. Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated? YES - Go to 12. NO - Intermittent misfire due to spark plug fouling, etc. (no misfire at this time).n

12. | Determine which cylinder(s) had the misfire. Does the misfire occur in the other cylinder whose spark plug was exchanged? YES - Replace the faulty spark plug.n NO - Go to 13.

13. | Turn the ignition switch OFF, and reset the ECM/PCM.

14. | Exchange the injector from the problem cylinder with one from the another cylinder.

15. | Let the engine idle for 2 minutes.

16. | Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

17. | Check the DTC or the Temporary DTC with the scan Tool. Is DTC or Temporary DTC P0301, P0302, P0303 or P0304 indicated? YES - Go to 18. NO - Intermittent misfire due to bad contact at the injector connector (no misfire at this time).n

18. | Determine which cylinder(s) had the misfire. Does the misfire occur in the other cylinder whose injector was exchanged? YES - Replace the faulty injector.n NO - Go to 19.

19. | Turn the ignition switch OFF.

20. | Disconnect the ignition coil 3P connector from the problem cylinder.

21. | Turn the ignition switch ON (II).

22. | Measure voltage between the ignition coil 3P connector terminal No. 3 and body ground. Is there battery voltage? YES - Go to 23. NO - Repair open or short in the wire between the No. 7 (15A), (No. 9 (15A))* fuse and the ignition coil. *: rear ignition coil n

23. | Check the compression. Is the engine compression? YES - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n NO - Repair the engine.n

24. | Turn the ignition switch OFF.

25. | Disconnect the negative cable from the battery.

26. | Disconnect ECM/PCM connector B (24P).

27. | Reconnect the negative cable to the battery.

28. | Turn the ignition switch ON (II).

29. | Measure voltage between body ground and the appropriate ECM/PCM connector terminal (see table).
PROBLEM CYLINDER | DTC | ECM/PCM TERMINAL | WIRE COLOR
--- | --- | --- | ---
No. 1 | P0301 | B5 | BRN
No. 2 | P0302 | B4 | RED
No. 3 | P0303 | B3 | BLU
No. 4 | P0304 | B2 | YEL
Is there battery voltage? YES - Go to 30. NO - Go to 38.

30. | Turn the ignition switch OFF, and remove the engine cover.

31. | Disconnect the injector 2P connector on the problem cylinder.

32. | Measure the resistance between the injector 2P connector terminals No. 1 and No. 2. Is there 10 W-13W? YES - Go to 33. NO - Replace the injector.n

33. | Exchange the injector from the problem cylinder with one from another cylinder.

34. | Let the engine idle for 2 minutes.

35. | Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.

36. | Check the DTC or the Temporary DTC with a scan tool. Is DTC or Temporary DTC P0301, P0302, P0303, or P0304 indicated? YES - Go to 37. NO - Intermittent misfire due to injector malfunction etc.n

37. | Determine which cylinder(s) had the misfire. Does the misfire occur in the other cylinder whose injector was exchanged? YES - Replace the faulty injector.n NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n

38. | Turn the ignition switch OFF and remove the engine cover.

39. | Disconnect the injector 2P connector on the problem cylinder.

40. | Turn the ignition switch ON (II).

41. | Measure voltage between the injector 2P connector terminal No. 1 and body ground. Is there battery voltage? YES - Go to 42. NO - Repair open in the wire between the injector and the PGM-FI main relay.n

42. | Turn the ignition switch OFF.

43. | Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).
PROBLEM CYLINDER | DTC | ECM/PCM TERMINAL | WIRE COLOR
--- | --- | --- | ---
No. 1 | P0301 | B5 | BRN
No. 2 | P0302 | B4 | RED
No. 3 | P0303 | B3 | BLU
No. 4 | P0304 | B2 | YEL
Is there continuity? YES - Repair short in the wire between the ECM/ PCM and the injector.n NO - Go to 44.

44. | Connect the appropriate injector 2P connector terminal No. 2 to body ground with a jumper wire (see table).
PROBLEM CYLINDER | DTC | WIRE COLOR
--- | --- | ---
No. 1 | P0301 | BRN
No. 2 | P0302 | RED
No. 3 | P0303 | BLU
No. 4 | P0304 | YEL

45. | Check for continuity between body ground and the appropriate ECM/PCM connector terminal (see table).
PROBLEM CYLINDER | DTC | ECM/PCM TERMINAL | WIRE COLOR
--- | --- | --- | ---
No. 1 | P0301 | B5 | BRN
No. 2 | P0302 | B4 | RED
No. 3 | P0303 | B3 | BLU
No. 4 | P0304 | B2 | YEL
Is there continuity? YES - Replace the injector, then recheck.n NO - Repair open in the wire between the ECM/ PCM and the injector.n