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

DTC P0301:  No. 1 Cylinder Misfire Detected
  
  
DTC P0303:  No. 3 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).

2.Clear the DTC with the HDS.

3.Start the engine, and let it idle without load (in Park or neutral).

4.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 9.


NO - If the screen indicates PASSED, go to 5. If the screen indicates EXECUTING, let the engine idle until a result comes on. If the screen indicates OUT OF CONDITION, 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 9.


NO - Go to 6.


6.Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
  • Engine speed
  • VSS
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

7.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 9.


NO - If the screen indicates PASSED, go to 8. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to 6 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 9.


NO - Intermittent failure, system is OK at this time. Check for loose wires or poor connections in the fuel system circuit.n


9.Turn the ignition switch OFF.

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
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

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 13.


NO - Intermittent misfire due to poor contact at the ignition coil connector (no misfire at this time). Make sure the coil connections are secure.n


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, then go to 40.


NO - Go to 14.


14.Turn the ignition switch OFF.

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
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

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 18.


NO - Intermittent misfire due to spark plug fouling (no misfire at this time).n

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 40.


NO - Go to 19.


19.Turn the ignition switch OFF.

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
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

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 24.


NO - Intermittent misfire due to bad contact in the injector connector (no misfire at this time). Check for poor connections or loose terminals at the injector.n


24.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 40.


NO - Go to 25.

25.Do an engine compression and a cylinder leakdown test.

Did the engine pass both tests?


YES - Go to 26.


NO - Repair the engine, then go to 40.


26.Do the VTEC rocker arm test.

Did the engine pass the test?


YES - Go to 27.


NO - Repair the VTEC rocker arm, then go to 40.


27.Turn the ignition switch OFF.

28.Jump the SCS line with the HDS.

29.Disconnect ECM/PCM connector C (44P).

30.Turn the ignition switch ON (II).

31.Measure voltage between body ground and the appropriate ECM/PCM connector terminal of the problem cylinder (see table).

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 C5 BRN 
No. 2 P0302 C6 RED 
No. 3 P0303 C7 BLU 
No. 4 P0304 C8 YEL 

 

Is there battery voltage?


YES - Go to 39.


NO - Go to 32.

32.Turn the ignition switch OFF.

33.Disconnect the injector 2P connector from the problem cylinder.

34.Turn the ignition switch ON (II).

35.Measure voltage between injector 2P connector terminal No. 1 and body ground.

 

Is there battery voltage?


YES - Go to 36.


NO - Repair open in the wire between the injector and PGM-FI main relay 1 (C), then go to 40.


36.Turn the ignition switch OFF.

37.Check for continuity between body ground and the appropriate ECM/PCM connector terminal of the problem cylinder (see table).

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 C5 BRN 
No. 2 P0302 C6 RED 
No. 3 P0303 C7 BLU 
No. 4 P0304 C8 YEL 

 

Is there continuity?


YES - Repair short in the wire between the ECM/ PCM and the injector, then go to 40.


NO - Go to 38.

38.Check for continuity between appropriate injector 2P connector terminal No. 2 and the appropriate ECM/PCM connector terminal of the problem cylinder (see table).

PROBLEM CYLINDER DTC ECM/PCM TERMINAL WIRE COLOR 
No. 1 P0301 C5 BRN 
No. 2 P0302 C6 RED 
No. 3 P0303 C7 BLU 
No. 4 P0304 C8 YEL 

 

Is there continuity?


YES - Go to 39.


NO - Repair open in the wire between the ECM/ PCM and the injector, then go to 40.

39.At injector side, measure resistance between injector 2P connector terminals No. 1 and No. 2.

 

Is there 10-13 W?


YES - Go to 50.


NO - Replace the injector, then go to 40.

40.Turn the ignition switch OFF.

41.Reconnect all connectors.

42.Turn the ignition switch ON (II).

43.Reset the ECM/PCM with the HDS.

44.Clear the crank pattern with the HDS.

45.Do the ECM/PCM idle learn procedure.

46.Do the crank pattern learn procedure.

47.Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
  • Engine speed
  • VSS
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

48.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0301, P0302, P0303, or P0304 is indicated, check for poor connections or loose terminals at the ignition coil, the injector, and the ECM/PCM, then go to troubleshooting DTC P0300, P0301, P0302, P0303 or P0304. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Go to 49.


49.Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?


YES - Troubleshooting is complete.n


NO - If the screen indicates FAILED, check for poor connections or loose terminals at the ignition coil, the injector, and the ECM/PCM, then go to 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to 47 and recheck.

50.Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.

51.Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
  • Engine speed
  • VSS
  • TP SENSOR A
  • CLV (calculated load value)
  • APP SENSOR A

52.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0301, P0302, P0303, or P0304 is indicated, check for poor connections or loose terminals at the ignition coil, the injector, and the ECM/PCM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM.n