LEMON Manuals: Even more car manuals for everyone
Home >> Chrysler >> 2003 >> PT Cruiser Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0300: Multiple Cylinder Misfire, DTC P0301: Cylinder #1 Misfire, DTC P0302: Cylinder #2 Misfire, DTC P0303: Cylinder #3 Misfire Or DTC P0304: Cylinder #4 Misfire >> Testing

DTC P0300: Multiple Cylinder Misfire, DTC P0301: Cylinder #1 Misfire, DTC P0302: Cylinder #2 Misfire, DTC P0303: Cylinder #3 Misfire Or DTC P0304: Cylinder #4 Misfire: Testing

  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, go to step  18.
  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 wire from the spark plug. Before continuing, inspect the ignition wire for damage or carbon tracking. Replace as necessary. Install a spark tester to the ignition wire. While cranking the engine, observe the spark coming from the spark tester. A crisp Blue spark should be generated that is able to jump the gap of the spark tester. Is good spark present? If yes, go to next step. If no, go to step  14.
  4. 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.
    5. 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.
  5. Install a fuel pressure gauge. Start the engine and observe the fuel pressure reading. Fuel pressure specification is 53-63 psi (366-434 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.
    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. 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 Tool (6539). Attach a fuel pressure test gauge to the "T" fitting on fuel line adapter. Start the engine and allow the fuel system to reach maximum pressure. Turn the ignition off. Fuel specification is 53-63 psi (366-434 kPa). Using Miller Special Tool 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.
    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.
    CAUTION: After each actuation of the fuel injector, start the engine to clear the cylinder of fuel. Failure to do so could cause engine damage.
  7. Remove hose clamp pliers. Install a fuel pressure gauge to the fuel rail. Start the engine and allow the fuel pressure to reach maximum pressure. Turn the engine off, leaving the ignition on. 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  9.
  8. 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  18.

  9. Turn the ignition off. Disconnect the fuel injector harness connector. 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 ASD relay output circuit at the fuel injector harness connector. Does the test light illuminate brightly? If yes, go to next step. If no, repair the ASD relay output circuit.
  10. Turn the ignition off. Disconnect the fuel injector harness connector. Ignition on, engine not running. Using a 12-volt test light connected to 12 volts, 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 fuel injector harness connector. Disconnect the PCM harness connectors. Check the injector control circuit. Was a problem found with the injector control circuit? If yes, repair the injector control circuit. If no, visually inspect both the component and the PCM connectors. Look for damage, partially broken wires and backed out or corroded terminals. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
    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 fuel line adapter. 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 53-63 psi (366-434 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. Turn the ignition off. Remove the ignition wire. Measure the resistance of the ignition wire. Is the resistance below 10 k/ohms? If yes, go to next step. If no, replace the ignition wire.
  15. Turn the ignition off. Disconnect the ignition coil harness connector. 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 ASD relay output circuit at the ignition coil harness connector. Does the test light illuminate brightly? If yes, go to next step. If no, repair the ASD relay output circuit.
  16. Turn the ignition off. Disconnect the ignition coil harness connector. 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.
    17. 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.
  17. Turn the ignition off. Disconnect the ignition coil harness connector. Disconnect the PCM harness connectors. Check the coil control circuit. Was a problem found with the coil control circuit? If yes, repair the coil control circuit. If no, before continuing disconnect the PCM harness connector and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
    18. WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.
    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.
    NOTE: The conditions that set the DTC are not present at this time.
  18. Refer to any Technical Service Bulletins (TSBs) that may apply. Review the DRBIII® scan tool freeze frame information. If possible, try to duplicate the conditions under which the DTC set. With the engine running at normal operating temperature, monitor the DRBIII® scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals. Inspect and clean all PCM, engine, and chassis grounds. 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. Were any of the above conditions present? If yes, repair as necessary. If no, test complete.
scientia non olet · About LEMON Manuals