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Home >> Dodge and Ram >> 2023 >> ProMaster 2500 >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> 3.6L - DTCS P0202 To P0330 >> DTC Troubleshooting >> P0300-Multiple Cylinder Misfire >> Diagnostic Test

Diagnostic Test

  1. CHECK FOR AN ACTIVE CONDITION 
    1. Turn the ignition on.
    2. With the scan tool, read and record all DTCs and Freeze Frame information.
    3. Operate the vehicle under conditions recorded in the Freeze Frame information when the DTC was set.
      NOTE:

      During the test drive of the vehicle, note when the misfire condition is present for use later in this diagnostic test. Also monitor the Downstream O2 Sensor(s) when the misfire is occurring. O2 Sensor voltage readings that are consistently on the low side of the scale would indicate a lean condition. This could indicate a lack of fuel due to a plugged Fuel Injector or fuel system issue. O2 Sensor voltage readings that are consistently on the high side of the scale indicates that the Catalytic Converter is burden with too much fuel. This could be caused by a lack of spark or a possible leaky Fuel Injector.

      NOTE:

      Keep in mind that during a severe misfire (MIL Light flashing) the PCM will disable the Fuel Injector of the affected cylinder(s) for a calibrated number of engine revolutions to prevent damage to the Catalytic Converter. This can cause a misfire that occurs only at high engine speed or heavy engine load to appear to continue when returning to idle. However this could be due to the Fuel Injector being disabled until the rev counter resets.

    4. With the scan tool, view the Misfire Monitor to see which cylinders are effected.

      Are there excessive misfires occurring at this time?

      Yes 

      • Go To  2

      No 

  2. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.

      Are there any fuel, ignition system component, air handling component, VVT system, or VVL system DTCs active or pending?

      Yes 

      No 

      • Go To  3
  3. CHECK FOR MECHANICAL CONDITIONS THAT COULD CAUSE A MISFIRE 
    NOTE:

    Each of the following conditions can cause a misfire during most operating conditions with the exception of the out of balance tires or warped brake rotors.

    1. Visually inspect the engine for any of the following conditions:
      • Worn, loose or slipping serpentine belt. Refer to BELT, SERPENTINE, DIAGNOSIS AND TESTING .
      • Binding or misaligned engine driven accessories: Examples: A/C Compressor, P/S Pump, Water pump, etc.
      • Improper mounting of the CKP Sensor or damaged target wheel.
      • Harmonic Balancer out of balance.
      • Extremely out of balance tires or warped brake rotors.

      Were any of the above conditions present?

      Yes 

      No 

      • Go To  4
  4. CHECK THE ENGINE OIL AND OILING SYSTEM 
    NOTE:

    The VVT or VVL systems depend on sufficient oil pressure to operate normally. An oiling system or oil pressure issue can cause the VVT or VVL systems to operate erratically which can effect Camshaft timing or valve lift and cause a misfire during any operating condition.

    1. Turn the ignition off.
    2. The following items should be checked before continuing with this procedure. Failure to do so may lead to misdiagnosis.
      • LOW ENGINE OIL LEVEL
      • AERATED ENGINE OIL
      • INCORRECT ENGINE OIL FILTER (DOES NOT MEET OEM SPECIFICATIONS)
      • DETERIORATED OR DIRTY OIL
      • CONTAMINATED ENGINE OIL
      • INCORRECT ENGINE OIL VISCOSITY

      Were any of the above conditions present?

      Yes 

      • Repair the engine oiling or mechanical condition (i.e. improper oil drain back, oil sludge, damaged oil pump, pick-up tube or seal, etc.).
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK THE ENGINE OIL PRESSURE AND OIL PUMP OPERATION 
    1. Install the applicable adaptor to the oil filter cap and install an oil pressure gauge to the adaptor. If the adaptor is not available, monitor the oil pressure reading with the scan tool.
    2. Start the engine and allow it to idle.
    3. Monitor the engine oil pressure reading on the gauge or scan tool.
      NOTE:

      If the oil pressure is below 14.0 psi or oscillating excessively, it can cause a delay in Cam Phaser movement sufficient enough to cause a misfire during any operating condition.

      Is the oil pressure reading stable and above 14.0 psi?

      Yes 

      • Go To  6

      No 

      • Repair the engine oiling or mechanical condition (i.e. improper oil drain back, oil sludge, damaged oil pump, pick-up tube or seal, etc.).
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  6. CHECK THE VVT SYSTEM AND CAM PHASER POSITIONS 
    NOTE:

    A VVT system issue from a lack of oil pressure will generally effect all of the cylinders for both banks. If a Cam Phaser or Oil Control Valve is stuck, it will generally effect the cylinders on the bank where that Camshaft is located. This may be accompanied by a Crankshaft/Camshaft Timing Misalignment and/or Camshaft Position Slow Response DTC.

    1. If the multiple cylinder misfire is coming from the cylinders on the same bank and the VVT system is suspected to be the issue, check the VVT operation as follows:
      • With the scan tool, monitor and compare the suspect Intake and Exhaust Camshaft desired  position values with the Camshaft actual  position values with the engine running at idle. After comparing the two values at idle, check and compare the values at several different engine speeds. The best way to do this is to raise the engine speed quickly and hold steady for up to 30 seconds and monitor the actual and desired values. Then lower the engine speed and hold steady at a level above idle (off of lock pin) for up to 30 seconds and monitor the actual and desired values. Repeat this a few times up and down, monitoring the values and then allow the engine to come back to idle and monitor the actual position to verify that the phaser is coming back to lock pin. There are a few things to monitor during testing:
      • One is for the phaser not coming back to lock pin at idle (this could indicate a faulty phaser or oil control valve that is permanently stuck off lock pin or a VVT Solenoid that is electrically stuck on). For the standard 3.6L application  , lock pin position for the Intake Camshaft is 127.0 degrees and lock pin position for the Exhaust Camshaft is 117.0 degrees. For the 3.6L Upgrade application  , lock pin position for the Intake Camshaft is 146.0 degrees and lock pin position for the Exhaust Camshaft is 123.0 degrees.
      • A second is for the actual position lagging or moving slowly toward the desired position (this could indicate a faulty phaser or tarnished oil control valve that is dragging). The third thing to monitor for would be the actual position lagging and then overshooting the desired position (this could indicate a faulty phaser, oil control valve or VVT Solenoid that is intermittently sticking or binding and then overshoot when the condition goes away).
      • The third thing to monitor for would be the actual position lagging and then overshooting the desired position (this could indicate a faulty phaser, oil control valve or VVT Solenoid that is intermittently sticking or binding and then overshoot when the condition goes away).

      Is the difference between the actual value and the desired value readings more than 6.0 degrees at idle or is the actual value lagging behind or overshooting the desired value?

      Yes 

      • If the difference is greater than 6.0 degrees at idle, it is indicating that the camshaft will not return to lock pin. If the actual reading is lagging or overshooting when changing the engine speeds, it is indicating a binding or sticking. Diagnose and repair the issue with the VVT system. Performing the appropriate Camshaft Position Slow Response DTC diagnostic procedure (P000A - P000D) may aid in further diagnosing the system.

      No 

      • Go To  7
  7. CHECK THE INTAKE SYSTEM FOR LEAKS OR RESTRICTIONS 
    1. Visually inspect the intake plumbing for restriction. Check the Air Filter for excessive debris causing a restriction.
    2. Check the engine components and vacuum hoses for vacuum leaks.
      NOTE:

      A vacuum leak can affect one or more cylinders depending on the location of the leak.

      Were any issues found with the intake system?

      Yes 

      No 

      • Go To  8
  8. CHECK THE EXHAUST SYSTEM FOR RESTRICTIONS 
    1. Visually inspect the exhaust system for any physical damage that may cause a restriction and excessive exhaust back flow.
    2. Start the engine and allow it to idle.
    3. Check the exhaust flow at the tail pipe.

      Were any issues found with the exhaust system?

      Yes 

      No 

      • Go To  9
  9. CHECK THE FUEL QUALITY AND ETHANOL LEVEL 
    1. Check the fuel for the following:
      • Water in fuel
      • Correct type of fuel
      • Old or contaminated fuel
      • Low fuel
      • Perform the CHECK FOR PROPER ETHANOL LEVEL IN THE GASOLINE procedure. Refer to DIAGNOSIS AND TESTING .

      Were any problems found with the fuel?

      Yes 

      • Replace the fuel and, if necessary, flush and clean the fuel system.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  10
  10. CHECK THE FUEL DELIVERY SYSTEM 
    NOTE:

    Fuel pressure that is too high or too low will affect multiple cylinders and generally cause a misfire during most operating conditions.

    1. Perform the CHECKING THE FUEL DELIVERY SYSTEM test procedure. Refer to CHECKING THE FUEL DELIVERY SYSTEM (HARD START) .

      Were any problems found?

      Yes 

      • Perform the appropriate repair in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  11
  11. CHECK FOR A FUEL INJECTOR ISSUE 
    NOTE:

    A Fuel Injector that is plugged and spraying too little fuel, or fouled and spraying too much fuel or has an uneven pattern will generally cause a misfire during any operating condition. One faulty Fuel Injector will usually cause a single cylinder misfire. However if the injector is spraying an excessive amount of fuel, the excess fuel could also affect the adjoining cylinders. In most cases there will be far more misfire counts on the cylinder with the faulty Fuel Injector than on the other affected cylinders.

    CAUTION:

    After each Fuel Injector actuation, start the engine to clean the cylinder of fuel. Failure to do so could cause engine damage.

    1. Turn the ignition on and allow the fuel pressure to reach maximum pressure.
      NOTE:

      The ignition may need to be cycled on and off a couple times to reach maximum fuel pressure in the rail.

    2. Turn the ignition on.
    3. With the scan tool, actuate the Fuel Injector for the cylinders that indicated a misfire.
    4. Monitor the fuel pressure gauge.
    5. Restore the fuel pressure in the rail and repeat this step with two or three Fuel Injectors on cylinders that do not have a misfire. Compare the fuel pressure drop readings of the known good cylinders to the cylinders with the misfire condition.

      Did the fuel pressure gauge indicate a drop in fuel pressure equal to the pressure drop in the known good injectors?

      Yes 

      • Go To  12
        NOTE:

        Turn the ignition off, remove the Fuel Pressure Decay Tester and connect the fuel lines before continuing.

      No 

      • If the pressure drop is too little, check for debris in the Fuel Rail or Fuel Injector and repair as necessary. If the pressure drop is too large, suspect a faulty or fouled Fuel Injector as the issue.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  12. CHECK FOR PROPER SPARK AT THE IGNITION COILS 
    NOTE:

    A faulty Ignition Coil or Spark Plug can cause a misfire at idle but could also misfire only under a heavy load on the engine. One faulty Ignition Coil or Spark Plug will usually cause a single cylinder misfire, not a multiple cylinder misfire.

    1. Remove the Ignition Coil from the cylinders that are misfiring.
    2. Connect the Ignition Coil harness connector.
    3. Disconnect the Fuel Injector harness connector of the cylinder being tested.
    4. Install a spark tester on the Ignition Coil.
    5. 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 from the Ignition Coil.

      Is good spark present?

      Yes 

      • Go To  13

      No 

      • Go To  18
  13. INSPECT THE SPARK PLUG 
    1. Turn the ignition off.
    2. Remove the Spark Plug(s) in accordance with the Service Information. Refer to SPARK PLUG, REMOVAL .
    3. Inspect the Spark Plug(s) for the following conditions:
      • Cracks
      • Carbon Tracking
      • Fouling due to oil, coolant or excess fuel in the cylinder
      • Gap size out of specifications
      • Loose or broken electrode

      Check for signs of oil or coolant in the cylinder.

      Were any of the above conditions present?

      Yes 

      • Replace the Spark Plug in accordance with the Service Information. If oil or coolant were found in the cylinder, diagnose and repair the cause.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  14
  14. CHECK THE ENGINE COMPRESSION TO CHECK FOR VALVETRAIN OR COMBUSTION CHAMBER ISSUES 
    NOTE:

    A cylinder compression or valvetrain issue will cause a misfire during all operating conditions. These types of failures will normally affect a single cylinder. However, depending on the type of failure incurred, other cylinders can also be affected and show misfires. In most cases there will be far more misfire counts on the cylinder with the issue than on the other affected cylinders.

    NOTE:

    If you suspect that the VVT system is causing the issue, it may be helpful to perform the Camshaft Position Slow Response diagnostic procedures for the bank that the misfires are occurring on.

    1. Perform a cylinder compression test on all of the cylinders and compare the known good cylinders to the cylinders that are misfiring. Refer to DIAGNOSIS AND TESTING .

      Is the cylinder compression within specification?

      Yes 

      • Go To  15

      No 

      • Perform a Cylinder Leak Down Test to determine if the cause is from the valvetrain or combustion chambers and repair as necessary.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  15. EXCHANGE SPARK PLUG(S) AND CHECK FOR MISFIRE TO FOLLOW THE SPARK PLUG 
    1. Turn the ignition off.
    2. Exchange the Spark Plug(s) with a known good cylinder that was not indicating a misfire or replace the Spark Plugs if they are difficult to access.
    3. Start the engine and monitor the misfire monitor screen.

      Did the misfire switch to the previously good cylinder or go away if the Spark Plug(s) was replaced?

      Yes 

      • Replace the Spark Plugs in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  16
  16. CHECK THE EGR SYSTEM 
    NOTE:

    The EGR Valve should only allow flow during light to normal acceleration and steady speed states. There should be no EGR flow at idle. If the EGR Valve is stuck open or leaking, it will cause the engine to run rough and misfire at idle and hesitation on initial throttle tip in. The misfire should go away or decrease greatly when driving since EGR gas flow is normally allowed under those conditions.

    1. If the EGR Valve is suspected of leaking it can be checked as follows:
      • If the engine has a tube coming off of the EGR Valve, allow the vehicle to sit and cool to ambient temperature or until the EGR Tube is cooled to ambient temperature. Start the engine and allow it to idle in park. The EGR Valve should be closed at this time so there should be no flow of exhaust gases through the tube. If the EGR Valve is stuck open or leaking the tube will begin to heat up quickly from the exhaust gases leaking passed the valve.
      • If there is no tube coming off of the EGR Valve, or it is not easily accessible, block off the EGR Valve to stop flow into the engine. The most effective way of doing this is to loosen the bolts connecting the EGR Valve to the engine and slide a piece of metal or cardboard between the valve to block the opening. Tighten the bolts enough to form a good seal and start the engine to see if the misfire/rough running at idle is gone.

      Were any issue found with the EGR Valve?

      Yes 

      • Replace the EGR Valve in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  17
  17. CLEAN THE CARBON FROM THE VALVETRAIN AND COMBUSTION CHAMBERS 
    NOTE:

    Carbon build up on the engine valves and guides can cause a misfire during all operating conditions but is usually more noticeable during cruising speeds or heavy engine load conditions. If carbon build up is becoming an issue it could set only a single cylinder misfire but usually will affect more than one cylinder and set multiple cylinder misfire as well.

    1. Using the Mopar Combustion cleaner, de-carbon the valves and combustion chambers.
    2. After driving and clearing the combustion cleaner from the engine, erase any DTCs with the scan tool.
    3. Test drive the vehicle in accordance with the Freeze Frame data.
    4. With the scan tool, view the Misfire Monitor.

      Did the misfire return?

      Yes 

      • Go To  22

      No 

      • Cleaning the valves and combustion chambers repaired the fault.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  18. CHECK THE ASD RELAY OUTPUT CIRCUIT 
    1. Turn the ignition off.
    2. Disconnect the Ignition Coil harness connector.
    3. Turn the ignition on.
    4. With a scan tool, actuate the ASD Relay.
    5. 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?

      Yes 

      • Go To  19

      No 

      • Repair the open or short to ground in the ASD Relay Output circuit between the PDC and Ignition Coil harness connector.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
        • NOTE:

        Stop All Actuations.

  19. CHECK THE IGNITION COIL DRIVER CIRCUIT OPERATION 
    WARNING:

    When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

    1. Using a 12-volt test light connected to a 12 volt source, probe the Coil Control circuit at the Ignition Coil harness connector.
    2. Crank the engine for 5.0 seconds while observing the test light.

      What is the condition of the test light while cranking the engine?

      Brightly blinking 

      • Replace the Ignition Coil in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      ON constantly 

      • Go To  20

      OFF constantly 

      • Go To  21
  20. CHECK THE COIL CONTROL CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
    2. Disconnect the PCM C2 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 the GPEC Diagnostic Adaptor to perform the diagnosis.

    3. Connect the adapter.

      (special tool #10436, Adapter, GPEC Diagnostic)

    4. Check for continuity between ground and the Coil Control circuit at the Ignition Coil harness connector.

      Is there continuity between ground and the Coil Control circuit?

      Yes 

      No 

      • Go To  22
  21. CHECK THE COIL CONTROL CIRCUIT FOR AN OPEN 
    1. Turn the ignition off.
    2. Disconnect the PCM C2 harness connector.
    3. Measure the resistance of the Coil Control circuit between the Ignition Coil harness connector and the GPEC Adaptor.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  22

      No 

      • Repair the Coil Control circuit for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  22. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Perform any Service Bulletins that apply.
    2. Disconnect all PCM harness connectors.
    3. Disconnect all related in-line harness connections (if equipped).
    4. Disconnect the related component harness connectors.
    5. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
      • Proper connector installation.
      • Damaged connector locks.
      • Corrosion.
      • Other signs of water intrusion.
      • Weather seal damage (if equipped).
      • Bent terminals.
      • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
      • Terminals that have been pushed back into the connector cavity.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    9. With the scan tool, erase DTCs.
    10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    11. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No 

      • The wiring or poor connection problem has been repaired.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
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