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Home >> Dodge and Ram >> 2003 >> Durango Base, 5.9 Z, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 17 (Engine Controls - Self-Diagnostics - 3.9L & 5.9L) >> 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.
  1. Read and record the FREEZE FRAME DATA. Select OBD II MONITORS. Read and record the MIS-FIRE SIMILAR CONDITIONS WINDOW DATA. With these screens, attempt to duplicate the condition(s) that set this DTC. When the vehicle is operating in the SIMILAR CONDITIONS WINDOW, refer to the WHICH CYLINDER IS MISFIRING screen. Observe 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.
    NOTE: When a misfire is detected for a particular cylinder, the PCM will shut down that cylinder's injector control circuit.
  2. Visually inspect the engine for any of the following conditions; worn serpentine belt, binding engine-driven accessories, like the A/C compressor, P/S pump, water pump. Also check for misalignment in the water pump, P/S pump and A/C compressor pulleys. Check for corroded PCM power and ground circuits. Check for improper CKP, CMP, MAP, and TP sensor mounting. Also check for a poor connector/terminal to component connection. i.e., CKP sensor, fuel injector, ignition coil, etc. Then check for vacuum leaks, restricted air induction system or exhaust system. 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. Turn ignition on, with engine off. With the DRBIII(R) 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. Connect the ignition coil harness connector. Disconnect the ignition wire from the spark plug. Before continuing inspect the ignition wire for damage or carbon tracking. Replace as necessary. Install a spark tester on the ignition wire. 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 . 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 conditions 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. See FUEL SYSTEM PRESSURE RELEASE  .
  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. Fuel pressure within specification, go to next step. Fuel pressure below specification, go to step  12 . Fuel pressure 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. See FUEL SYSTEM PRESSURE RELEASE  .
    NOTE: Before continuing, visually and physically inspect the fuel delivery system for external leaks or damage. Repair or replace as necessary.
  7. Turn the ignition off. Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module. Install special Fuel Line Adapter 5/16" (6539) or 3/8" (6631) and the fuel pressure gauge between the fuel supply line and the fuel pump module. 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), pinch the rubber fuel line 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 fuel 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. See FUEL SYSTEM PRESSURE RELEASE  .
    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. Turn ignition on, with engine off. Using the DRBIII(R) 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:
    • Engine Vacuum - Must Be At Least 13 In. Hg In Neutral
    • Engine Valve Timing - Must Be Within Specification
    • Engine Compression - Must Be Within Specification
    • Engine Exhaust System - Must Be Free Of Any Restrictions Or Leaks
    • Engine PCV System - Must Flow Freely
    • Torque Converter Stall Speed - Must Be Within Specifications
    • Power Brake Booster - No Internal Vacuum Leaks
    • Fuel - Must Be Free Of Contamination
    • Cam Lobes - Must Not Be Worn Excessively
    • Cylinder Leakage Test - Must Be Within Specifications
    • Valve Springs - Cannot Be Weak Or Broken
    Are there any engine mechanical problems? If yes, repair as necessary. If no, go to step  17 .
  10. Turn the ignition off. Disconnect the fuel injector harness connector. Turn ignition on, with engine off. When a misfire is detected for a particular cylinder, the PCM will shut down that cylinders injector control circuit. With the DRBIII(R) scan tool, erase DTCs. Using a 12-volt test light connected to 12-volts, probe the injector control circuit. With the DRBIII(R) 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. 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  17 .
    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. See FUEL SYSTEM PRESSURE RELEASE  .
  12. Turn the ignition off. Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module. Install special Fuel Line Adapter 5/16" (6539) or 3/8" (6631) and the fuel pressure gauge between the fuel supply line and the fuel pump module. Turn ignition on, with engine off. With the DRBIII(R) scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge. Fuel pressure specification is 44-54 psi (300-368 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. See FUEL SYSTEM PRESSURE RELEASE  .
  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. If no problem is found, replace the fuel pump module.
    14. NOTE: If the vehicle being tested does not have an ignition coil wire answer YES to this test and continue.
  14. Turn the ignition off. Remove the ignition coil wire. Measure the resistance of the ignition coil wire. Is the resistance less than 10 k/ohms? If yes, go to next step. If no, replace the ignition coil wire.
  15. Turn the ignition off. 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 second while observing the test light. Does the test light brightly blink/flicker? If yes, replace the ignition coil. If no, go to next step.
  16. 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.
    17. NOTE: Before continuing, disconnect the PCM harness connectors and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary.
  17. 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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