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DTC P0300 - Random Misfire Detected

  1. Turn ignition on with engine off. Install scan tool to data link connector and check for DTCs. If DTC P0300 is present and fuel is at least 87 octane, go to next step. If fuel octane is less than 87, refuel with 87 or higher octane fuel and retest. If DTC P0300 is not present, problem is intermittent. See INTERMITTENTS in TESTS W/O CODES article.
  2. Disconnect ignition coil connector and measure voltage between ground and ignition coil harness connector terminal No. 3 (Black/White wire). If 12 volts exists, go to next step. If 12 volts does not exist, repair open in wire between ignition switch and ignition coil.
  3. Turn ignition off and disconnect ECM harness connector. Measure resistance between ignition coil harness connector terminal No. 1 (Blue/Yellow wire) and ECM harness connector terminal No. 52 (Blue/Yellow wire). If resistance is less than 2 ohms, go to next step. If resistance is more than 2 ohms, repair open in Blue/Yellow wire between ignition coil and ECM.
  4. Check continuity between ground and ignition coil harness connector terminal No. 1 (Blue/Yellow wire). If continuity does not exist, go to next step. If continuity exists, repair short to ground in Blue/Yellow wire between ignition coil and ECM.
  5. Measure resistance between ignition coil harness connector terminal No. 2 (Brown/Red wire) and ECM harness connector terminal No. 25 (Brown/Red wire). If resistance is less than 2 ohms, go to next step. If resistance is more than 2 ohms, repair open in Brown/Red wire between ignition coil and ECM.
  6. Check continuity between ground and ignition coil harness connector terminal No. 2 (Brown/Red wire). If continuity does not exist, go to next step. If continuity exists, repair short to ground in Brown/Red wire between ignition coil and ECM.
  7. Turn ignition off and disconnect ignition coil connector. Measure resistance of primary ignition coils across coil connector terminals No. 1 (Blue/Yellow wire) and No. 3 (Black/White wire), and terminals No. 2 (Brown/Red wire) and No. 3 (Black/White wire). If primary coil resistance is approximately 500 ohms, go to next step. If primary coil resistance is not approximately 500 ohms, replace ignition coil.
  8. Measure resistance of secondary ignition coils across spark plug terminals No. 1 and 4 and across spark plug wire terminals No. 2 and 3. If secondary coil resistance is 10.3k-13.9k ohms, inspect ignition wires, fuel injectors, and vacuum hoses. If all components are undamaged and within specifications, clear DTC and retest. If resistances not with in parameters, replace ignition coil.
  9. After repairs, clear DTC. See CLEARING CODES under SELF-DIAGNOSTIC SYSTEM in TESTS W/CODES - INTRODUCTION article. Retest system. If DTC does not reset, system is okay.
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