## 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 a 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 HDS or 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 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 HDS or the scan Tool. Is DTC or a 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). Make sure the injector connection is secure. Check for poor connections or loose terminals at the injector.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 - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/ PCM.n NO - Repair the engine.n

24. | Turn the ignition switch OFF.

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

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

27. | 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 28. NO - Go to 36.

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

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

30. | Measure the resistance between the injector 2P connector terminals No. 1 and No. 2. Is there 10 W-13W? YES - Go to 31. NO - Replace the injector.n

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

32. | Let the engine idle for 2 minutes.

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

34. | Check the DTC or the Temporary DTC with the HDS or the scan tool. Is DTC or Temporary DTC P0301, P0302, P0303, or P0304 indicated? YES - Go to 35. NO - Intermittent misfire due to injector malfunction etc. Make sure the injector connections are secure. Check for poor connections or loose terminals at the injector connector.n

35. | 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 - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/ PCM.n

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

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

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

39. | Measure voltage between the injector 2P connector terminal No. 1 and body ground. Is there battery voltage? YES - Go to 40. NO - Repair open in the wire between the injector and the PGM-FI main relay.n

40. | Turn the ignition switch OFF.

41. | 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 42.

42. | 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

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 - Replace the injector, then recheck.n NO - Repair open in the wire between the ECM/PCM and the injector.n