DTC Troubleshooting: P0300 (75) and some of P0301 (71), P0302 (72), P0303 (73), P0304 (74)

DTC P0300:	Random Misfire and Any Combination of the Following:
DTC P0302:	No. 2 Cylinder Misfire
DTC P0304:	No. 4 Cylinder Misfire

• If the misfiring is frequent enough to trigger detection of increased emissions during 2 consecutive driving cycles, the MIL will come on, and DTC P0300 (and some combination of P0301 through P0304) will be stored.
• If the misfiring is frequent enough to damage the catalyst, the MIL will blink whenever the misfiring occurs, and DTC P0300 (and some combination of P0301 through P0304) will be stored. When the misfiring stops, the MIL will remain on.
• Troubleshoot the following DTCs first if any of them were stored along with the random misfire DTC(s):
  P0068, P0106, P0107, P0108: Manifold absolute pressure (MAP) sensor
  P0171, P0172: Fuel system
  P0201-P0204, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271: Injector
  P0335, P0339: Crankshaft position (CKP) sensor
  P0342, P0343, P0344: Camshaft position (CMP) sensor
  P0351-P0358: Ignition coil
  P0506, P0507: Idle control system
  P0401, P0403, P0404, P0405, P0406, P0409, P0489, P0490: Exhaust gas recirculation (EGR) system

1.	Record the following freeze data. Engine speed Vehicle speed Throttle position CLV

2.	Do the DTC CLEAR in the CLEAR MENU with the HDS.

3.	Start the engine with no load (in neutral), then let it idle.

4.

Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS. Is it FAILED? YES - Go to 9. NO - If it is PASSED, go to 5. If it is EXECUTING, keep the driving condition continually until a result comes on. If it is 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 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 the recorded freeze data.

7.	Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS. Is it FAILED? YES - Go to 9. NO - If it is PASSED, go to 8. If it is EXECUTING, keep the driving condition continually until a result comes on. If it is 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 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.n

9.	Turn the ignition switch OFF.

10.	Check fuel quality. Is the quality good? YES - Go to 11. NO - Drain the fuel from the fuel tank and fill with known-good fuel, then go to 15.

11.	Inspect the spark plugs. If the spark plugs are fouled or worn, replace them.

12.	Test-drive the vehicle for several minutes in the range of the recorded freeze data.

13.	Check the CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE in the DATA LIST for 10 minutes with the HDS. Does CYL1 MISFIRE, CYL2 MISFIRE, CYL3 MISFIRE and/or CYL4 MISFIRE show misfire counts? YES - Go to 14. NO - Go to 15.

14.

Check the fuel pressure. Is the fuel pressure OK? YES - Go to 15. NO - If the pressure is too high, replace the fuel pressure regulator, then go to 15. If the pressure is too low, check the fuel pump, the fuel feed pipe, and the fuel filter. If there are OK, replace the fuel pressure regulator, then go to 15.

15.	Turn the ignition switch ON (II).

16.	Do the ECM RESET in the CLEAR MENU with the HDS.

17.	Do the ETCS learn procedure.

18.	Test-drive the vehicle for several minutes in the range of the recorded freeze data.

19.

Check for Temporary DTCs or DTCs in the DTCs MENU with the HDS. Are any Temporary DTCs or DTCs indicated? YES - If DTC P0300, P0301, P0302, P0303 or P0304 is indicated, 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. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC troubleshooting. NO - Go to 20.

20.

Monitor the OBD STATUS for DTC P0301, P0302, P0303 or P0304 in the DTCs MENU with the HDS. Is it PASSED? YES - Troubleshooting is complete.n NO - If it is FAILED, then go to 1 and recheck. If it is EXECUTING, keep the driving condition continually until a result comes on. If it is Out of CONDITION, go to 18 and recheck.