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Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
  1. 1)  CYLINDER MIS-FIRE CONDITION ACTIVE 

    Engine running.

    Observe the WHICH CYLINDER IS MISFIRING screen for at least one minute with a scan tool.

    Is there a misfire present at this time? 

    Yes 

    1. Go To step  2).

    No 

    1. Refer to INTERMITTENT CONDITION .
    2. Perform POWERTRAIN VERIFICATION TEST .
  2. 2)  VISUAL 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 inspect the engine for any of the following conditions.

    - Worn serpentine belt

    - Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.

    - Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys

    - Corroded PCM power and ground circuits.

    - Improper CKP, CMP, MAP, and TP Sensor mounting

    - Poor connector/terminal to component connection. i.e, CKP sensor, Fuel Injector, Ign coil, etc.

    - Vacuum leaks

    - Restricted Air Induction system or Exhaust system.

    - Internal engine component failures.

    Were any of the above conditions present? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  3).
  3. 3)  (F42), (A15) ASD RELAY OUTPUT CIRCUIT 
    Fig 1: Checking ASD Relay Output at Ignition Coil No. 6
    GC0002797Courtesy of DAIMLERCHRYSLER CORP.
    Fig 2: Checking ASD Relay Output At Fuel Injector No. 6
    GC0002758Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the No.6 Ignition Coil harness connector.

    Disconnect the No.6 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 (F42), (A15) ASD Relay Output circuit in the Ignition Coil harness connector and Fuel Injector harness connector while the relay is actuating.

    Does the test light illuminate brightly? 

    Yes 

    1. Go To step  4).

    No 

    1. Repair the excessive resistance or short to ground in the (F42), (A15) ASD Relay Output circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .
  4. 4)  IGNITION SYSTEM OPERATION 

    Turn the ignition off.

    Connect the Ignition Coil No.6 harness connector.

    Remove the Ignition Coil.

    Leave the Fuel Injector harness connector of the cylinder being tested disconnected.

    Install a spark tester on the Ignition Coil.

    While cranking the engine observe the spark coming from the spark tester.

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

    Is good spark present? 

    Yes 

    1. Go To step  5).

    No 

    1. Go To step  14).
      NOTE: Connect the Fuel Injector harness connector before continuing.
  5. 5)  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 conditions present? 

    Yes 

    1. Replace the Spark Plug.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  6).
  6. 6)  FUEL PRESSURE CHECK 
    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 to the fuel rail.

    Start the engine and observe the fuel pressure reading.

    Choose a conclusion that best matches your fuel pressure reading. 

    Within Specification 

    1. Go To step  7).

    Below Specification 

    1. Go To step  12).

    Above Specification 

    1. Replace the fuel filter/pressure regulator.
    2. Perform POWERTRAIN VERIFICATION TEST .
      NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
  7. 7)  FUEL PRESSURE 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. Failure to follow these instructions can result in personal injury or death

    Install special tool #6539 (5/16") or #6631 (3/8") fuel line adapter.

    Install the fuel pressure gauge.

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

    Turn the ignition off.

    NOTE: Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).

    Using special tool #C4390, Hose Clamp Pliers, pinch the rubber fuel line between the fuel pressure gauge and the engine.

    Monitor the fuel pressure gauge for a minimum of 5 minutes.

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

    Does the pressure fall below the listed specification? 

    Yes 

    1. Replace the leaking Fuel Injector(s).
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  8).
  8. 8)  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 Fuel Injector actuation, start the engine to clean the cylinder of fuel. Failure to do so could cause engine damage.

    Remove special tool #C4390.

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

    Ignition on, engine not running.

    Using the scan tool, actuate the No.6 Fuel Injector.

    Monitor the fuel pressure gauge.

    Does the fuel pressure gauge indicate a drop in fuel pressure? 

    Yes 

    1. Go To step  9).

    No 

    1. Go To step  10).
      NOTE: Turn the ignition off, remove the Fuel Pressure gauge, and connect the fuel lines before continuing.
  9. 9)  ENGINE MECHANICAL 

    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

    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? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  17).
  10. 10)  FUEL INJECTOR 
    Fig 3: Checking Fuel Injector
    GC0002759Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the No.6 Fuel Injector harness connector.

    Ignition on, engine not running.

    NOTE: When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinders Injector Control circuit.

    With the scan tool, erase DTCs.

    Using a 12-volt test light connected to 12-volts, probe the (K58) Injector Control No.6 circuit.

    With the scan tool, actuate the Fuel Injector.

    Does the test light blink/flicker? 

    Yes 

    1. Replace the Fuel Injector.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  11).
  11. 11)  (K58) INJECTOR CONTROL NO.6 CIRCUIT 
    Fig 4: Checking Injector Control No. 6 Circuit
    GC0002761Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the C2 PCM harness connector.

    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.

    Check the (K58) Injector Control No.6 circuit for an open, short to ground, and short to voltage.

    Was a problem found with the (K58) Injector Control No.6 circuit? 

    Yes 

    1. Repair the excessive resistance or short in the (K58) Injector Control No.6 circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  17).
  12. 12)  FUEL SUPPLY LINE RESTRICTED 

    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 tool #6539 (5/16") #6631(3/8") fuel line adapter and the fuel pressure gauge between the fuel supply line and the fuel pump module.

    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 407 KPa +/- 34 KPa (59 psi +/- 5 psi).

    Is the fuel pressure within specification? 

    Yes 

    1. Repair or replace fuel supply line as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  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 POWERTRAIN VERIFICATION TEST .

    No 

    1. Before continuing, check the Fuel Pump Module harness connector terminals for corrosion, damage, or terminal push out. Make sure the ground circuit is functional. Repair as necessary. Replace the Fuel Pump Module.
    2. Perform POWERTRAIN VERIFICATION TEST .
  14. 14)  IGNITION WIRE 
    NOTE: If the vehicle being tested does not have an ignition wire answer YES to this test and continue.

    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 step  15).

    No 

    1. Replace the Ignition Wire.
    2. Perform POWERTRAIN VERIFICATION TEST .
  15. 15)  IGNITION COIL 
    Fig 5: Checking Ignition Coil
    GC0002798Courtesy of DAIMLERCHRYSLER CORP.

    Disconnect the No.6 Ignition Coil harness connector.

    Remove the Fuel Pump Relay.

    Using a 12-volt test light connected to 12-volts, probe the (K10) Coil Control No.6 circuit.

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

    NOTE: The primary resistance of the 3.7L and 4.7L Ignition coil is 0.6 to 0.9 of an ohm at 77°F (25°C).

    Does the test light brightly blink/flicker? 

    Yes 

    1. Replace the Ignition Coil.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  16).
  16. 16)  (K10) COIL CONTROL NO.6 CIRCUIT 
    Fig 6: Checking Coil Control No. 6 Circuit
    GC0002799Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the C2 PCM harness connector.

    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.

    Check the (K10) Coil Control No.6 circuit for an open, short to ground, and short to voltage.

    Was a problem found with the (K10) Coil Control No.6 circuit? 

    Yes 

    1. Repair the (K10) Coil Control No.6 circuit.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  17).
  17. 17)  PCM 
    NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

    Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

    Were there any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
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