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Home >> Chrysler >> 2006 >> PT Cruiser Base, 2D Convertible, Standard >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> 1.6L Engine - DTCS P0303 To P0629 >> Diagnosis And Testing >> P0304-Cylinder 4 Misfire >> Diagnostic Test

Diagnostic Test

  1. 1)  CHECKING FOR CYLINDER MIS-FIRE CONDITION PRESENT 
    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: Reviewing the vehicle repair history may aid in the repair of the misfire condition.

    Engine running.

    Observe the WHICH CYLINDER IS MISFIRING screen and identify the cylinders that have a misfire present.

    Is there a misfire present at this time? 

    Yes 

    1. Go To  2).

    No 

    1. Refer to the INTERMITTENT CONDITION diagnostic procedure.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  2. 2)  VISUAL AND PHYSICAL INSPECTION 
    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 cylinders Injector Control circuit.

    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, Ign coil, etc.

    - Vacuum leaks

    - Restricted Air Induction system

    NOTE: Verify the integrity of the powers and grounds for the PCM.

    Were any of the above conditions present? 

    Yes 

    1. Repair as necessary.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  3).
  3. 3)  IGNITION SYSTEM OPERATION 

    Turn the ignition off.

    Disconnect the Ignition wire from the spark plug.

    NOTE: 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.

    NOTE: A crisp blue spark should be generated that is able to jump the gap of the spark tester.

    Is good spark present? 

    Yes 

    1. Go To  4).

    No 

    1. Go To  14).
  4. 4)  SPARK PLUG 

    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

    NOTE: 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? 

    Yes 

    1. Replace the Spark Plug.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  5).
  5. 5)  CHECKING FUEL PRESSURE 
    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. Failure to follow these instructions can result in personal injury or death.

    Install a fuel pressure gauge.

    Start the engine and observe the fuel pressure reading.

    NOTE: Fuel pressure specification is 400 KPa +/- 34 KPa (58 psi +/- 5 psi).

    Choose a conclusion that best matches your fuel pressure reading. 

    Within Specification 

    1. Go To  6).

    Below Specification 

    1. Go To  12).

    Above Specification 

    1. Replace the fuel filter/pressure regulator.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  6. 6)  CHECKING FUEL LEAK DOWN 
    NOTE: Before continuing visually and physically inspect the fuel delivery system for external leaks or damage. Repair /replace as necessary.

    Turn the ignition off.

    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.

    Install special 5/16 fuel line adapter tool #6539.

    Attach a fuel pressure test gauge to the T fitting on the tool #6539

    Start the engine and allow the fuel system to reach maximum pressure.

    Turn the ignition off.

    NOTE: Fuel specification is 400 KPa +/- 34 KPa (58 psi +/- 5 psi).

    Using special tool #C4390, Hose Clamp Pliers, 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.

    NOTE: The pressure should not fall below 241 KPa (35 psi)

    Does the fuel pressure gauge fall below the above specification? 

    Yes 

    1. Replace the leaking Injector(s).
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  7).
  7. 7)  FUEL INJECTOR OPERATION 
    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. Failure to follow these instructions can result in personal injury or death.
    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.

    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 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? 

    Yes 

    1. Go To  8).

    No 

    1. Go To  9).
  8. 8)  CHECKING FOR POSSIBLE MECHANICAL PROBLEM 

    Check for any of the following conditions/mechanical problems.

    ENGINE VACUUM - must be at least 13 inches in neutral

    ENGINE VALVE TIMING - must be within specifications

    ENGINE COMPRESSION - must be within specifications

    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

    Are there any engine mechanical problems? 

    Yes 

    1. Repair as necessary.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Refer to the INTERMITTENT CONDITION diagnostic procedure.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  9. 9)  (K343) ASD RELAY OUTPUT CIRCUIT 
    Fig 1: Checking ASD Relay Output Circuit For Open At Fuel Injector Connector
    GC0041851Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the Fuel Injector harness connector.

    Ignition on, engine not running.

    With the scan tool, actuate the ASD Relay.

    Using a 12-volt test light connected to ground, probe the (K343) ASD Relay Output circuit at the Fuel Injector harness connector.

    Does the test light illuminate brightly? 

    Yes 

    1. Go To  10).

    No 

    1. Repair the (K343) ASD Relay Output circuit.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  10. 10)  FUEL INJECTOR 
    Fig 2: CHECKING FUEL INJECTOR CIRCUIT
    GC0041876Courtesy of DAIMLERCHRYSLER CORP.

    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 (K14) Injector Control circuit.

    With the scan tool, actuate the Fuel Injector.

    Does the test light blink/flicker? 

    Yes 

    1. Replace the Fuel Injector.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  11).
  11. 11)  INJECTOR CONTROL CIRCUIT 

    Turn the ignition off.

    Disconnect the Fuel Injector harness connector.

    Disconnect the PCM harness connectors.

    Check the (K14) Injector Control circuit.

    Was a problem found with the Injector Control circuit? 

    Yes 

    1. Repair the (K14) Injector Control circuit.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module in accordance with the Service Information. (Refer to STANDARD PROCEDURE - PCM/ECM/SKREEM PROGRAMMING) .
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  12. 12)  RESTRICTED FUEL SUPPLY LINE 

    Turn the ignition off.

    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. Failure to follow these instructions can result in personal injury or death.

    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 scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.

    NOTE: Fuel pressure specification is 400 KPa +/- 34 KPa (58 psi +/- 5 psi).

    Is the fuel pressure within specification? 

    Yes 

    1. Repair or replace fuel supply line as necessary.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  13).
  13. 13)  FUEL PUMP INLET STRAINER 

    Turn the ignition off.

    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. Failure to follow these instructions can result in personal injury or death.

    Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.

    Is the Fuel Inlet Strainer plugged? 

    Yes 

    1. Replace the Fuel Pump Inlet Strainer.
    2. Perform (STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. 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.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  14. 14)  IGNITION WIRE 

    Turn the ignition off.

    Remove the ignition wire.

    Measure the resistance of the ignition wire.

    Is the resistance below 10K ohms? 

    Yes 

    1. Go To  15).

    No 

    1. Replace the Ignition Wire.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  15. 15)  (K344) ASD RELAY OUTPUT CIRCUIT 
    Fig 3: Checking ASD Relay Output Circuit
    GC0041877Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the Ignition Coil harness connector.

    Ignition on, engine not running.

    With the scan tool, actuate the ASD Relay.

    Using a 12-volt test light connected to ground, probe the (K344) ASD Relay Output circuit at the Ignition Coil harness connector.

    Does the test light illuminate brightly? 

    Yes 

    1. Go To  16).

    No 

    1. Repair the (K344) ASD Relay Output circuit.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
  16. 16)  IGNITION COIL 
    Fig 4: Checking Ignition Coil Control Circuit
    GC0041878Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the Ignition Coil harness connector.

    Using a 12-volt test light connected to 12-volts, probe the (K19) Ignition Coil Control circuit.

    Crank the engine for 5 second while observing the test light.

    Does the test light blink/flicker? 

    Yes 

    1. Replace the Ignition Coil.
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Go To  17).
  17. 17)  COIL CONTROL CIRCUIT 

    Turn the ignition off.

    Disconnect the Ignition Coil harness connector.

    Disconnect the PCM harness connector.

    Check the (K19) Coil Control circuit.

    Was a problem found with the Coil Control circuit? 

    Yes 

    1. Repair the (K19) Coil Control circuit.
    2. Perform (STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .

    No 

    1. Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module in accordance with the Service Information. (Refer to STANDARD PROCEDURE - PCM/ECM/SKREEM PROGRAMMING)
    2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
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