DTC Troubleshooting
DTC Troubleshooting: P0300 (75)
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
- Pressure Gauge Adapter 07NAJ-P07010A
- A/T Low Pressure Gauge w/Panel 07406-0070301
- A/T Pressure Test Hose 07AAJ-PY4A100
- A/T Pressure Adapter 07MAJ-PY40120
- Oil Pressure Hose 07ZAJ-S5AA200
NOTE:
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information Initial Inspection and Diagnostic Overview.
- If the misfire is frequent enough to trigger detection of increased emissions during two consecutive driving cycles, the MIL comes on, and DTC P0300 (and some of the combination of P0301 through P0304) are 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) are stored. When the misfire stops, the MIL stays 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 (Because parts can sometimes fail without setting DTCs, you should also do a physical inspection of the systems listed below.):
P0101, P0102, P0103: MAF sensor
P0107, P0108, P1128, P1129: MAP sensor
P0171, P0172: Fuel system
P0365, P0369: CMP sensor B
P0506, P0507: Idle control system
P2646, P2647, P2648, P2649: VTEC system
1. Turn the ignition switch to ON (II).
2. Clear the DTC with the HDS.
3. Start the engine, and let it idle without load (in P or N).
4. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, go to step 5. If the HDS indicates EXECUTING, keep idling until a result comes on. If the HDS indicates OUT OF CONDITION, wait for several minutes, then 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 step 9.
NO -
Go to step 6.
6. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- Vehicle speed
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
7. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS indicate FAILED?
YES -
Go to step 9.
NO -
If the HDS indicates PASSED, go to step 8. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 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 step 9.
NO -
Intermittent failure, the system is OK at this time.
9. Turn the ignition switch to LOCK (0).
10. Check the fuel quality.
Is the quality good?
YES -
Go to step 11.
NO -
Drain the tank and fill it with a known-good fuel, then go to step 19.
11. Remove and inspect the spark plugs Testing and Inspection. If the spark plugs are fouled or worn, replace them.
12. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- Vehicle speed
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
13. 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 19.
14. Check the fuel pressure Testing and Inspection.
Is the fuel pressure OK?
YES -
Go to step 15.
NO -
- If the fuel pressure is too high, replace the fuel pressure regulator Fuel Pressure Regulator Replacement, then go to step 19.
- 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 Fuel Pressure Regulator Replacement, then go to step 19.
15. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
16. Check under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 176 °F (80 °C)
- Transmission in P or N
- All electrical loads off
17. Monitor the ENGINE SPEED in the DATA LIST with the HDS. Raise and hold the engine speed steady at 2,500±100 rpm. While holding the engine speed steady, check the MAF SENSOR in the DATA LIST with the HDS.
Is about 8.6-10.5 g/s indicated?
YES -
Go to step 18.
NO -
Replace MAF sensor/IAT sensor 1 MAF Sensor/IAT Sensor 1 Replacement, then go to step 19.
18. Perform the VTEC rocker arm test VTEC Rocker Arm Test.
Does the engine pass the VTEC rocker arm test?
YES -
Replace the injectors Service and Repair, then go to step 19.
NO -
Repair the VTEC system, and then go to step 19.
19. Turn the ignition switch to ON (II).
20. Reset the PCM with the HDS.
21. Do the PCM idle learn procedure PCM Idle Learn Procedure.
22. Do the CKP pattern clear/CKP pattern learn procedure.
23. Test-drive the vehicle for several minutes in the range of these recorded freeze data parameters:
- ENGINE SPEED
- Vehicle speed
- REL TP SENSOR
- CLV (calculated load value)
- APP SENSOR
24. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0300, P0301, P0302, P0303, or P0304 indicated?
YES -
Check for poor connections or loose terminals at the ignition coil, the injector, and the PCM, then go to the troubleshooting for DTC P0301, P0302, P0303, or P0304 DTC Troubleshooting.
NO -
Go to step 25.
25. Monitor the OBD STATUS for DTC P0301, P0302, P0303, or P0304 in the DTCs MENU with the HDS.
Does the HDS indicate PASSED?
YES -
Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 24, go to the indicated DTC's troubleshooting.
NO -
If the HDS indicates FAILED, go to step 1 and recheck. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 23.