DTC Troubleshooting: P0300 (75) and any combination of P0301 (71), P0302 (72), P0303 (73), P0304 (74)
DTC P0300:
 Random Misfire and Any Combination of the Following:
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
Special Tools Required

Oil pressure gauge attachment
 07NAJ-P070100

Low pressure gauge
 07406-0070002

Oil pressure hose
 07ZAJ-S5A0200
NOTE:
  • Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
  • If the misfire is frequent enough to trigger detection of increased emissions during two consecutive driving cycles, the MIL will come on, and DTC P0300 (and some of the combination of P0301 through P0304) will be stored.
  • If the misfire is frequent enough to damage the catalyst, the MIL will flash whenever the misfire occurs, and DTC P0300 (and some of the combination of P0301 through P0304) will be stored. When the misfire stops, the MIL will remain on.
  • If any of the DTCs listed below are indicated at the same time as the random misfire DTCs, troubleshoot those DTCs first, then recheck for random misfire DTCs:
    P0102, P0103: Mass air flow (MAF) sensor
    P0107, P0108: Manifold absolute pressure (MAP) sensor
    P0171, P0172: Fuel system
    P0335, P0339: Crankshaft position (CKP) sensor
    P0365, P0369: Camshaft position (CMP) sensor B
    P2646, P2647, P2648, P2649: VTEC system
  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 driving until a result comes on. If the screen indicates OUT OF CONDITION, wait for several minutes, then 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
  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 the 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.■
  1. Turn the ignition switch OFF.
  1. Check the fuel quality.
Is the quality good?
YES -
Go to Step 11 .
NO -
Drain the tank and fill with a known-good fuel, then go to Step 24 .
  1. Inspect the spark plugs. If the spark plugs are fouled or worn, replace them.
  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 14 .
NO -
Go to Step 24 .
  1. Check the fuel pressure.
Is the fuel pressure OK?
YES -
Go to Step 15 .
NO -
  • If the fuel pressure is too high, replace the fuel pressure regulator, then go to Step 24 .
  • If the fuel pressure is too low, check the fuel pump, the fuel feed pipe, and the fuel filter. If they are OK, replace the fuel pressure regulator, then go to Step 24 .
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Check for these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 80 °C (176 °F)
    • Transmission in neutral
    • All electrical loads off
  1. Monitor the ENGINE SPEED in the DATA LIST with the HDS, and hold the engine speed at 4,500 rpm (min −1 ). Once the engine speed is met, hold the accelerator pedal steady for more than 10 seconds.
Did the engine speed vary more than 100 rpm (min −1 ) from 4,500 rpm (min −1 )?
YES -
Repeat Step 17 .
NO -
Go to Step 18 .
  1. While holding the engine speed at 4,500 rpm (min −1 ), check the MAF SENSOR in the DATA LIST with the HDS.
Is there about 14−20 gm/s?
YES -
Go to Step 19 .
NO -
Replace the MAF sensor/IAT sensor, then go to Step 24 .
  1. Turn the ignition switch OFF.
  1. Remove the rocker arm oil pressure switch (A) (or the bolt), and install the special tools as shown, then install the rocker arm oil pressure switch (A) (or the bolt) in the pressure gauge attachment (B).
    NOTE: Install the rocker arm oil pressure switch (or the bolt) in the reverse order of removal with a new O-ring.
  1. Reconnect the rocker arm oil pressure switch 2P connector.
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. Check the oil pressure at engine speeds of 1,000 rpm (min −1 ) and 2,000 rpm (min −1 ).
Is the oil pressure below 49 kPa (0.5 kgf/cm 2 , 7 psi)?
YES -
Check for air in the fuel line, then go to Step 24 .
NO -
Inspect the VTEC system, then go to Step 24 .
  1. Turn the ignition switch ON (II).
  1. Reset the ECM with the HDS.
  1. Clear the CKP pattern with the HDS.
  1. Do the ECM idle learn procedure.
  1. Do the CKP pattern learn procedure.
  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 for Temporary DTCs or DTCs with the HDS.
Are DTC P0300, P0301, P0302, P0303, or P0304 indicated?
YES -
Check for poor connections or loose terminals at the ignition coil, the injector, and the ECM, then go to troubleshooting DTC P0301, P0302, P0303, or P0304.
NO -
Go to Step 31 .
  1. 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. If any other Temporary DTCs or DTCs were indicated in Step 30 , go to the indicated DTC's troubleshooting.■
NO -
If the screen indicates FAILED, check for poor connections or loose terminals at the ignition coil, the injector, and the ECM, then go to Step 1 . If the screen indicates EXECUTING, keep driving until a comes on. If the screen indicates OUT OF CONDITION, go to Step 29 .