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.
  1. Turn the ignition switch ON (II).
  1. Clear the DTC with the HDS.
  1. Start the engine, and let it idle without load (in neutral).
  1. Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES -
Go to Step 9 .
NO -
If the screen indicates PASSED, go to Step 5 . If the screen indicates EXECUTING, keep idling until a result comes on. If the screen indicates OUT OF CONDITION, wait for several minutes, and recheck.
  1. 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 .
  1. 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 A
  1. Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES -
Go to Step 9 .
NO -
If the screen indicates PASSED, go to Step 8 . If the screen indicates EXECUTING, keep driving until a result comes on. If he screen indicates OUT OF CONDITION, go to Step 6 and recheck.
  1. 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.■
  1. Turn the ignition switch OFF.
  1. Remove the intake manifold cover.
  1. 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 42 .
  1. Turn the ignition switch OFF.
  1. Exchange the ignition coil from the problem cylinder with one from another cylinder.
  1. 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
  1. 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). Make sure the coil connections are secure.■
  1. 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, then go to Step 60 .
NO -
Go to Step 17 .
  1. Turn the ignition switch OFF.
  1. Exchange the spark plug from the problem cylinder with one from another cylinder.
  1. 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
  1. 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).■
  1. 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 60 .
NO -
Go to Step 22 .
  1. Turn the ignition switch OFF.
  1. Exchange the injector from the problem cylinder with one from the another cylinder.
  1. Start the engine, and let it idle for 2 minutes.
  1. 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
  1. 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 bad contact at the injector connector (no misfire at this time). Check for poor connections or loose terminals at the injector.■
  1. Determine which cylinder had the misfire.
Does the misfire occur in the cylinder where the injector was exchanged?
YES -
Replace the faulty injector, then go to Step 60 .
NO -
Go to Step 28 .
  1. Turn the ignition switch OFF.
  1. Disconnect the ignition coil 3P connector from the problem cylinder.
  1. Turn the ignition switch ON (II).
  1. Measure voltage between ignition coil 3P connector terminal No. 3 and body ground.
Is there battery voltage?
YES -
Go to Step 32 .
NO -
Repair open in the wire between the ignition coil and the ignition coil relay, then go to Step 60 .
  1. Turn the ignition switch OFF.