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Home >> Dodge and Ram >> 2003 >> Durango Base, 5.9 Z, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 15 (Engine Controls - Self Diagnostics - 4.7L) >> Diagnostic Tests >> DTC P0300: Multiple Cylinder Misfire, DTC P0301: Cylinder #1 Misfire, DTC P0302: Cylinder #2 Misfire, DTC P0303: Cylinder #3 Misfire, DTC P0304: Cylinder #4 Misfire, DTC P0305: Cylinder #5 Misfire, DTC P0306: Cylinder #6 Misfire, DTC P0307: Cylinder #7 Misfire Or DTC P0308: Cylinder #8 Misfire >> Testing

DTC P0300: Multiple Cylinder Misfire, DTC P0301: Cylinder #1 Misfire, DTC P0302: Cylinder #2 Misfire, DTC P0303: Cylinder #3 Misfire, DTC P0304: Cylinder #4 Misfire, DTC P0305: Cylinder #5 Misfire, DTC P0306: Cylinder #6 Misfire, DTC P0307: Cylinder #7 Misfire Or DTC P0308: Cylinder #8 Misfire: Testing

WARNING: This page is about a different car, the 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Check for any TSB's that apply to a Misfire condition. Review the vehicle repair history for any misfire condition repairs that have been performed.
NOTE: When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinders injector control circuit.
  1. With the DRBIII® scan tool, select DTCs and related functions. Read and record the freeze frame data. Select OBD-II Monitors, read and record the Misfire Similar Conditions Window Data. With these screens, attempt to duplicate the condition(s) that has set this DTC. When the vehicle is operating in the Similar Conditions Window, refer to the Which Cylinder Is Misfiring screen for at least one minute. Is there a misfire present? If yes, go to next step. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: Anything that affects the speed of the crankshaft can cause a misfire DTC. When a misfire is detected for a particular cylinder, the PCM will shut down that cylinders injector control circuit.
  2. Reviewing the vehicle repair history may aid in the repair of the misfire condition. Visually and physically inspect the engine for any of the following conditions, worn serpentine belt, binding engine-driven accessories, misaligned water pump, P/S pump and A/C compressor pulleys, improper CKP sensor mounting, poor connector/terminal to component connection. i.e., CKP sensor, fuel injector, ignition coil, etc., vacuum leaks, restricted air induction system. Ensure the powers and grounds for the PCM are operating properly. Were any of the above conditions present? If yes, repair as necessary. If no, go to next step.
  3. Turn the ignition off. Disconnect the ignition coil harness connector and fuel injector harness connector of the cylinder being tested. Ignition on, engine not running. With the DRBIII® scan tool, actuate the ASD relay. Using a 12-volt test light connected to ground, probe the (A142) ASD relay output circuit at the ignition coil harness connector and fuel injector harness connector. Does the test light illuminate brightly? If yes, go to next step. If no, repair the excessive resistance or short to ground in the (A142) ASD relay output circuit.
  4. Turn the ignition off. Remove the ignition coil. Connect the ignition coil harness connector. Before continuing, inspect the ignition coil for the following conditions. If a problem is found, replace the ignition coil. Damage or carbon tracking on the coil or the spark plug insulator boot. Install a spark tester on the ignition coil. While cranking the engine observe the spark coming from the spark tester. A crisp Blue spark that is able to jump the gap of the spark tester should be generated. Is good spark present? If yes, go to next step. If no, go to step  14.
    NOTE: Connect the fuel injector harness connector before continuing.
  5. Turn the ignition off. Remove the spark plug. Inspect the spark plug for the following conditions. Cracks, carbon tracking, foreign material, gap size out of specifications, loose or broke electrode. Lightly tap the bottom of the spark plug on a solid surface. The electrode in the spark plug should not move. Were any of the above condition present? If yes, replace the spark plug. If no, go to next step.
    6. WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
  6. Install a fuel pressure gauge. Start the engine and observe the fuel pressure reading. Fuel pressure specification is 44-54 psi (300-368 kPa). Choose a conclusion that best matches your fuel pressure reading. If the pressure is within specification go to next step. If the pressure is below specification go to step  12. If the pressure is above specification replace the fuel filter/pressure regulator.
    7. WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
  7. Before continuing visually and physically inspect the fuel delivery system for external leaks or, damage. Repair/replace as necessary. Turn the ignition off. Install special 5/16" Fuel Line Adapter (6539). Attach a fuel pressure test gauge to the "T" fitting on the Fuel Line Adapter. Start the engine and allow the fuel system to reach maximum pressure. Turn the ignition off. Fuel specification is 44-54 psi (300-368 kPa). Using Hose Clamp Pliers (C4390), slowly clamp off the rubber hose on the fuel pressure adapter between the fuel pressure gauge and the fuel pump module. Monitor the fuel pressure gauge for a minimum of 5 minutes. The pressure should not fall below 35 psi (241 kPa) Does the fuel pressure gauge fall below the above specification? If yes, replace the leaking injector(s). If no, go to next step.
    8. WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
    CAUTION: After each Fuel Injector actuation, start the engine to clean the cylinder of fuel. Failure to do so could cause engine damage.
  8. Remove Hose Clamp Pliers. Start the engine and allow the fuel pressure to reach maximum pressure. Ignition on, engine not running. Using the DRBIII® scan tool, actuate the fuel Injector for the cylinder that indicated the misfire. Monitor the fuel pressure gauge. Does the fuel pressure gauge indicate a drop in fuel pressure? If yes, go to next step. If no, go to step  10. Turn the ignition off, remove the fuel pressure gauge, and connect the fuel lines before continuing.
  9. Check for any of the following conditions/mechanical problems:
    • Ensure engine vacuum is at least 13 in. Hg with transmission in Neutral.
    • Ensure valve timing is within specification.
    • Ensure compression is within specification.
    • Ensure exhaust is free from restrictions or leaks.
    • Ensure PCV system flows freely.
    • Ensure torque converter stall speed is within specification.
    • Ensure power brake booster has no internal vacuum leaks.
    • Ensure fuel is not contaminated.
    • Ensure fuel injector is not plugged or restricted.
    • Ensure fuel injector harness connectors are connected to correct fuel injectors.

    Are there any engine mechanical problems? If yes, repair as necessary. If no, go to step  16.

  10. Turn the ignition off. Disconnect the fuel injector harness connector. Ignition on, engine not running. With the DRBIII® scan tool, erase DTCs. Using a 12-volt test light connected to ground, probe the injector control circuit. With the DRBIII® scan tool, actuate the fuel injector. Does the test light blink/flicker? If yes, replace the fuel injector. If no, go to next step.
    11. CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool (8815) to perform diagnosis.
  11. Turn the ignition off. Disconnect the PCM harness connectors. Check the injector control circuit for an open, short to ground and short to voltage. Was a problem found with the injector control circuit? If yes, repair the injector control circuit. If no, go to step  16.
    12. WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
  12. Turn the ignition off. Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module. Install special 5/16 Fuel Line Adapter Tool (6539) between the disconnected fuel line and the fuel pump module. Attach a fuel pressure test gauge to the "T" fitting on the tool (6539). Ignition on, engine not running. With the DRBIII® scan tool, actuate the ASD fuel system test and observe the fuel pressure gauge. Fuel pressure specification is 44-54 psi (305-373 kPa). Is the fuel pressure within specification? If yes, repair or replace fuel supply line as necessary. If no, go to next step.
    13. WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.
  13. Turn the ignition off. Remove the fuel pump module and inspect the fuel inlet strainer. Is the fuel inlet strainer plugged? If yes, replace the fuel pump inlet strainer. If no, before continuing, check the fuel pump module harness connector terminals for corrosion, damage, or terminal push out. Ensure the ground circuit is operating properly. Repair as necessary. Replace the fuel pump module.
  14. Disconnect the ignition coil harness connector. Remove the fuel pump relay or ASD relay. Using a 12-volt test light connected to 12-volts, probe the ignition coil control circuit. Crank the engine for 5 seconds while observing the test light. Does the test light blink/flicker? If yes, replace the ignition coil. If no, go to next step.
    15. CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool (8815) to perform diagnosis.
  15. Turn the ignition off. Disconnect the PCM harness connectors. Check the coil control circuit for an open, short to ground and short to voltage. Was a problem found with the coil control circuit? If yes, repair the coil control circuit. If no, go to next step.
    16. NOTE: Before continuing, disconnect the PCM harness connectors and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary.
  16. Using the wiring diagram as a guide, inspect the wire harness and connectors. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect both the component and the PCM connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
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