DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306: Random Misfire and Any Combination of the Following; No. 1 Cylinder Misfire Detected; No. 2 Cylinder Misfire Detected; No. 3 Cylinder Misfire Detected; No. 4 Cylinder Misfire Detected; No. 5 Cylinder Misfire Detected; No. 6 Cylinder Misfire Detected

Special Tools Required

Pressure gauge adapter 07NAJ-P07010A
A/T low pressure gauge w/panel 07406-0070300
A/T pressure hose 07406-0020201
A/T pressure hose, 2,210 mm 07MAJ-PY4011A
A/T pressure adapter 07MAJ-PY40120
Oil pressure hose 07ZAJ-S5A0200

NOTE:

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 combination of P0301 through P0306) will be stored.
If the misfire is frequent enough to damage the catalyst, the MIL will blink whenever the misfire occurs, and DTC P0300 (and some combination of P0301 through P0306) will be stored. When the misfire stops, the MIL will remain on.
Troubleshoot the following DTCs first, if any of them were stored along with the random misfire DTC(s):
Before you troubleshoot, record all freeze data and any on-board snapshot, and review the GENERAL TROUBLESHOOTING INFORMATION .

P0107, P0108, P1128, P1129: Manifold absolute pressure (MAP) sensor

P0171, P0172, P0174, P0175: Fuel system

P0335, P0339, P0385, P0389: Crankshaft position (CKP) sensor A/B

P0506, P0507: Idle control system

P0340, P0344: Camshaft position (CMP) sensor

P2646, P2647, P2648, P2649: VTEC system

P0401, P0404, P0406, P2413: Exhaust gas recirculation (EGR) system

Record all freeze data and any on-board snapshot with the HDS.
Clear the DTC with the HDS.
Start the engine (in Park or neutral), then let it idle without load.
Monitor the OBD STATUS for DTC P0301, P0302, P0303, P0304, P0305, or P0306 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
1. YES - Go to step 9.
2. 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.
Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE show misfire counts?
1. YES - Go to step 9.
2. NO - Go to step 6.
Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- Engine speed
- Engine coolant temperature
- Vehicle speed
- Throttle position
- CLV (calculated load value)
Monitor the OBD STATUS for DTC P0301, P0302, P0303, P0304, P0305, or P0306 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
1. YES - Go to step 9.
2. 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.
Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE show misfire counts?
1. YES - Go to step 9.
2. NO - Intermittent failure, system is OK at this time.
Turn the ignition switch OFF.
Check the fuel quality.
Is the quality good?
1. YES - Go to step 11.
2. NO - Drain the tank, and fill it with a known-good fuel, then go to step 20.
Inspect the spark plugs (see SPARK PLUG INSPECTION ). If the spark plugs are fouled or worn, replace them.
Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- Engine speed
- Engine coolant temperature
- Vehicle speed
- Throttle position
- CLV (calculated load value)
Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE in the DATA LIST for 10 minutes with the HDS.
Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE, CYL4 MISFIRE, CYL5 MISFIRE, and/or CYL6 MISFIRE show misfire counts?
1. YES - Go to step 14.
2. NO - Go to step 20.
Check the fuel pressure (see FUEL PRESSURE TEST ).
Is the fuel pressure OK?
1. YES - Go to step 15.
2. NO -
  - If the pressure is too high, replace the fuel pressure regulator (see FUEL PRESSURE REGULATOR REPLACEMENT ) then go to step 20.
  - If the 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 (see FUEL PRESSURE REGULATOR REPLACEMENT ), then go to step 20.
Turn the ignition switch OFF.
Remove the rocker arm oil pressure switch (VTEC oil pressure switch) (A), and install the special tools as shown, then install the rocker arm oil pressure switch (VTEC oil pressure switch) in the pressure gauge adapter (B).
NOTE: Install the switch in the reverse order of removal with a new O-ring.

Fig 1: Installing Rocker Arm Oil Pressure Switch In Pressure Gauge Adapter
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Reconnect rocker arm oil pressure switch (VTEC oil pressure switch) 2P connector.
Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
Check the oil pressure at engine speed of 1,000 and 2,000 rpm. Keep the measuring time as short as possible (less than 1 minute) because the engine is running without load.
Is the oil pressure below 49 kPa (0.5 kgf/cm ² , 7 psi) ?
1. YES - Check for air in the fuel line, then go to step 20.
2. NO - Inspect the VTEC system (see VTEC ROCKER ARM TEST ), then go to step 20.
Turn the ignition switch ON (II).
Reset the ECM/PCM with the HDS.
Clear the CKP pattern with the HDS.
Do the ECM/PCM IDLE LEARN PROCEDURE .
Do the CKP pattern learn procedure (see CRANK (CKP) PATTERN CLEAR/CRANK (CKP) PATTERN LEARN ).
Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- Engine speed
- Engine coolant temperature
- Vehicle speed
- Throttle position
- CLV (calculated load value)
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - If DTC P0301, P0302, P0303, P0304, P0305, or P0306 are indicated, check for poor connections or loose terminals at the ignition coil, the injector, and the PCM, then go to troubleshooting DTC P0301, P0302, P0303, P0304, P0305, or P0306, 2004-2005 models (see DTC P0301, P0302, P0303, P0304, P0305, P0306: NO. 1 CYLINDER MISFIRE DETECTED (2004-2005 MODELS); NO. 2 CYLINDER MISFIRE DETECTED (2004-2005 MODELS); NO. 3 CYLINDER MISFIRE DETECTED (2004-2005 MODELS); NO. 4 CYLINDER MISFIRE DETECTED (2004-2005 MODELS); NO. 5 CYLINDER MISFIRE DETECTED (2004-2005 MODELS); NO. 6 CYLINDER MISFIRE DETECTED (2004-2005 MODELS) ), 2006 model (see DTC P0301, P0302, P0303, P0304, P0305, P0306: NO. 1 CYLINDER MISFIRE DETECTED (2006 MODEL); NO. 2 CYLINDER MISFIRE DETECTED (2006 MODEL); NO. 3 CYLINDER MISFIRE DETECTED (2006 MODEL); NO. 4 CYLINDER MISFIRE DETECTED (2006 MODEL); NO. 5 CYLINDER MISFIRE DETECTED (2006 MODEL); NO. 6 CYLINDER MISFIRE DETECTED (2006 MODEL) ). If any other Temporary DTCs or DTCs are indicated, go to the indicated DTCs troubleshooting.
2. NO - Go to step 27.
Monitor the OBD STATUS for DTC P0301, P0302, P0303, P0304, P0305, or P0306 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
1. YES - Troubleshooting is complete.
2. NO - If the screen indicates FAILED, go to step 1. and recheck. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 25. and recheck.