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Home >> Honda >> 2000 >> S2000 >> Repair and Diagnosis >> Engine Performance >> System >> PGM-FI System >> DTC Troubleshooting >> 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

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:
  • Information marked with an asterisk (*) applies to 2000-2004 models.
  • Information marked with double asterisk (**) applies to 2005 model.
  • Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  1. After checking and recording the freeze data, reset the ECM (see HOW TO RESET THE ECM ). If there is no freeze data of the misfire, just clear the DTC.
  2. Start the engine, listen for a clicking sound at the injector at the problem cylinder.

    Does it click? 

    1. YES -  Go to step 3.
    2. NO -  Go to step  30.
  3. Turn the ignition switch OFF.
  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 for a DTC or Temporary DTC with a scan tool or the HDS.

    Is DTC P0301, P0302, P0303, or P0304, or Temporary DTC P1399* (P0301, P0302, P0303, or P0304)** indicated? 

    1. YES -  Go to step 7.
    2. NO -  Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time).
  7. Determine which cylinder(s) had the misfire.

    Does the misfire occur in the other cylinder where the ignition coil was exchanged? 

    1. YES -  Replace the faulty ignition coil.
    2. NO -  Go to step 8.
  8. Turn the ignition switch OFF.
  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 for DTC or Temporary DTC with a scan tool or the HDS.

    Is DTC P0301, P0302, P0303 or P0304, or Temporary DTC P1399* (P0301, P0302, P0303, or P0304)** indicated? 

    1. YES -  Go to step 12.
    2. NO -  Intermittent misfire due to spark plug fouling, etc. (no misfire at this time).
  12. Determine which cylinder had the misfire.

    Does the misfire occur in the other cylinder where the spark plug was exchanged? 

    1. YES -  Replace the faulty spark plug.
    2. NO -  Go to step 13.
  13. Turn the ignition switch OFF.
  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 for a DTC or Temporary DTC with a scan tool or the HDS.

    Is DTC P0301, P0302, P0303, or P0304, or Temporary DTC P1399* (P0301, P0302, P0303, or P0304)** indicated? 

    1. YES -  Go to step 18.
    2. NO -  Intermittent misfire due to bad contact in the injector connector (no misfire at this time).
  18. Determine which cylinder had the misfire.

    Does the misfire occur in the other cylinder where the injector was exchanged? 

    1. YES -  Replace the faulty injector (see INJECTOR REPLACEMENT  ).
    2. NO -  Go to step 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 ignition coil 3P connector terminal No. 3 and body ground.
    Fig 1: Measuring Voltage Between Ignition Coil 3P Connector Terminal No. 3 And Body Ground
    G03692639Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES -  Go to step 23.
    2. NO -  Repair open in the wire between the No. 4 IGN COIL (15 A) fuse and the ignition coil.
  23. Turn the ignition switch OFF.
  24. Check for continuity between ignition coil 3P connector terminal No. 2 and body ground.
    Fig 2: Checking Continuity Between Ignition Coil 3P Connector Terminal No. 2 And Body Ground
    G03692640Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES -  Go to step 25.
    2. NO -  Repair open in the wire between the ignition coil and G101.
  25. Disconnect ECM connector C (31P).
  26. Check for continuity between body ground and the ECM connector terminal (see table).
    Fig 3: Checking Continuity Between Body Ground And ECM Connector Terminal
    G03692641Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (1 Of 7)

    PROBLEM CYLINDER DTC ECM TERMINAL WIRE COLOR
    No. 1 P0301 C4 WHT
    No. 2 P0302 C12 WHT/GRN
    No. 3 P0303 C13 WHT/BLK
    No. 4 P0304 C14 WHT/BLU

    Is there continuity? 

    1. YES -  Repair short in the wire between the ECM and the ignition coil.
    2. NO -  Go to step 27.
  27. Connect appropriate ignition coil 3P connector terminal No. 1 to body ground with a jumper wire (see table).
    Fig 4: Connecting Appropriate Ignition Coil 3P Connector Terminal No. 1 To Body Ground With A Jumper Wire
    G03692642Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (2 Of 7)

    PROBLEM CYLINDER DTC WIRE COLOR
    No. 1 P0301 WHT
    No. 2 P0302 WHT/GRN
    No. 3 P0303 WHT/BLK
    No. 4 P0304 WHT/BLU
  28. Check for continuity between body ground and the ECM connector terminal (see table).
    Fig 5: Checking Continuity Between Body Ground And ECM Connector Terminal
    G03692643Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (3 Of 7)

    PROBLEM CYLINDER DTC ECM TERMINAL WIRE COLOR
    No. 1 P0301 C4 WHT
    No. 2 P0302 C12 WHT/GRN
    No. 3 P0303 C13 WHT/BLK
    No. 4 P0304 C14 WHT/BLU

    Is there continuity? 

    1. YES -  Go to step 29.
    2. NO -  Repair open in the wire between the ECM and the ignition coil.
  29. Check the engine compression.

    Is the engine compression OK? 

    1. YES -  Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the symptom/indication goes away, replace the original ECM (see ECM REPLACEMENT  ).
    2. NO -  Repair the engine.
  30. Turn the ignition switch OFF.
  31. Disconnect ECM connector B (25P).
  32. Turn the ignition switch ON (II).
  33. Measure voltage between body ground and the ECM connector terminal (see table).
    Fig 6: Measuring Voltage Between Body Ground And ECM Connector Terminal
    G03692644Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (4 Of 7)

    PROBLEM CYLINDER DTC ECM TERMINAL WIRE COLOR
    No. 1 P0301 B11 BRN
    No. 2 P0302 B3 RED
    No. 3 P0303 B4 BLU
    No. 4 P0304 B5 YEL

    Is there battery voltage? 

    1. YES -  Go to step 34.
    2. NO -  Go to step  42.
  34. Turn the ignition switch OFF.
  35. Disconnect the injector 2P connector from the problem cylinder.
  36. At the injector side, measure resistance between injector 2P connector terminals No. 1 and No. 2.
    Fig 7: Measuring Resistance Injector 2P Connector Terminals No. 1 And No. 2
    G03692645Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 10-13 Ω? 

    1. YES -  Go to step 37.
    2. NO -  Replace the injector (see INJECTOR REPLACEMENT  ).
  37. Exchange the injector from the problem cylinder with one from another cylinder.
  38. Let the engine idle for 2 minutes.
  39. Test-drive the vehicle several times in the range of the freeze data or under various conditions if there was no freeze data.
  40. Check for a DTC or Temporary DTC with a scan tool.

    Is DTC P0301, P0302, P0303, or P0304, or Temporary DTC P1399* (P0301, P0302, P0303, or P0304)** indicated? 

    1. YES -  Go to step 41.
    2. NO -  Intermittent misfire due to injector malfunction, etc.
  41. Determine which cylinder had the misfire.

    Does the misfire occur in the other cylinder where the injector was exchanged? 

    1. YES -  Replace the faulty injector.
    2. NO -  Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the symptom/indication goes away, replace the original ECM (see ECM REPLACEMENT  ).
  42. Turn the ignition switch OFF.
  43. Disconnect injector 2P connector from the problem cylinder.
  44. Turn the ignition switch ON (II).
  45. Measure voltage between injector 2P connector terminal No. 2 and body ground.
    Fig 8: Measuring Voltage Between Injector 2P Connector Terminal No. 2 And Body Ground
    G03692646Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES -  Go to step 46.
    2. NO -  Repair open in the wire between the injector and the PGM-FI main relay.
  46. Turn the ignition switch OFF.
  47. Check for continuity between body ground and the ECM connector terminal (see table).
    Fig 9: Checking Continuity Between Body Ground And ECM Connector Terminal
    G03692647Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (5 Of 7)

    PROBLEM CYLINDER DTC ECM TERMINAL WIRE COLOR
    No. 1 P0301 B11 BRN
    No. 2 P0302 B3 RED
    No. 3 P0303 B4 BLU
    No. 4 P0304 B5 YEL

    Is there continuity? 

    1. YES -  Repair short in the wire between the ECM and the injector.
    2. NO -  Go to step 48.
  48. Connect injector 2P connector terminal No. 1 to body ground with a jumper wire (see table).
    Fig 10: Connecting Injector 2P Connector Terminal No. 1 To Body Ground With A Jumper Wire
    G03692648Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (6 Of 7)

    PROBLEM CYLINDER DTC WIRE COLOR
    No. 1 P0301 BRN
    No. 2 P0302 RED
    No. 3 P0303 BLU
    No. 4 P0304 YEL
  49. Check for continuity between body ground and the ECM connector terminals (see table).
    Fig 11: Checking Continuity Between Body Ground And ECM Connector Terminals
    G03692649Courtesy of AMERICAN HONDA MOTOR CO., INC.
    ECM CONNECTOR TERMINALS (7 Of 7)

    PROBLEM CYLINDER DTC ECM TERMINAL WIRE COLOR
    No. 1 P0301 B11 BRN
    No. 2 P0302 B3 RED
    No. 3 P0303 B4 BLU
    No. 4 P0304 B5 YEL

    Is there continuity? 

    1. YES -  Replace the injector, then recheck.
    2. NO -  Repair open in the wire between the ECM and the injector.
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