P0300 on 2015-2019 Ram Promaster City: Random Misfire Causes and Fixes

What's Unique About the 2015-2019 Ram PROMASTER CITY

The 2.4L Tigershark engine in the Promaster City has two well-documented issues that directly lead to code P0300. First, the valve cover and its integrated spark plug tube seals frequently leak, allowing engine oil to flood the spark plug wells, which shorts out the ignition coils and causes misfires. Second, these engines are known for problems with excessive oil consumption, which can foul spark plugs over time, also resulting in misfires. A third, related issue is that the PCV valve is integrated into the valve cover; if the PCV valve fails, it can create a vacuum leak, but replacement requires changing the entire valve cover assembly.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Rough or shaking idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Reduced fuel economy
• Solid check engine light
• Flashing check engine light (indicating a severe misfire)
• Burning oil smell from oil dripping on hot engine components

Most Likely Causes

1. Oil in Spark Plug Wells from Leaking Gasket 🔴 High Probability → Shop Spark Plug The valve cover gasket and integrated spark plug tube seals are a very common failure point on the 2.4L Tigershark engine. The seals harden over time, allowing oil to seep into the wells, shorting out the ignition coils.
   How to confirm: Remove the ignition coils and look down into the spark plug tubes with a flashlight. The presence of liquid oil is definitive proof. The coil boots will be wet with oil.
   Typical fix: Replace the entire valve cover assembly. The new cover comes with a new gasket, new spark plug tube seals, and a new integrated PCV valve, addressing multiple potential failure points at once. While performing the repair, it is best practice to also replace the oil-soaked ignition coil boots and the spark plugs.
   Est. part cost: $60-$120 for a valve cover kit
2. Worn or Fouled Spark Plugs 🔴 High Probability → Shop Spark Plug Excessive oil consumption can foul the spark plugs, causing misfires. Additionally, they are a standard wear item with a service interval that is often neglected. Oil from a leaking valve cover gasket also ruins them.
   How to confirm: Remove the spark plugs and inspect them. Look for heavy carbon buildup, oil contamination on the electrode, or a worn-down electrode. The correct gap is 0.047 inches (1.2mm).
   Typical fix: Replace all four spark plugs. Use high-quality Iridium plugs like the OEM Mopar (Champion) or NGK Laser Iridium. Always verify the gap before installation.
   Est. part cost: $40-$80
3. Faulty Ignition Coils 🟡 Medium Probability → Shop Ignition Coil Ignition coils can fail from heat and vibration over time. Their failure is often accelerated by being soaked in oil from a leaking valve cover gasket.
   How to confirm: If you have a code for a specific cylinder (e.g., P0301) along with P0300, swap the ignition coil from that cylinder with another one. Clear the codes and drive the vehicle. If the misfire code follows the coil to the new cylinder, the coil is bad.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace them as a set if they are original and high-mileage, especially if they have been contaminated with oil.
   Est. part cost: $35-$70 per coil
4. Needs PCM Software Update ⚪ Low Probability For 2019 models specifically, FCA issued a Technical Service Bulletin (TSB #18-068-19) to address false misfire codes (P0300-P0304) by reprogramming the Powertrain Control Module (PCM).
   How to confirm: A Ram dealership or a properly equipped independent shop can check your vehicle's VIN to see if this TSB applies and if the update has been performed.
   Typical fix: The dealer reprograms the PCM with the latest software. This is not a DIY repair.
   Est. part cost: $0 if under warranty, otherwise $100-$200 for labor

Rare But Worth Checking

• Faulty PCV Valve: → Shop PCV Valve A PCV valve that is stuck open can create a significant vacuum leak, leading to a lean condition and random misfires. On the 2.4L Tigershark, the PCV valve is integrated into the valve cover and is not sold separately for most model years. If it fails, the entire valve cover must be replaced.
• Low Engine Compression due to Internal Wear: The 2.4L Tigershark engine is subject to a warranty extension for excessive oil consumption which can, in severe cases, be caused by internal issues like piston rings. If you have high oil consumption and misfires, this is a possibility.
• Clogged or Faulty Fuel Injectors: → Shop Fuel Injector While less common than ignition issues, dirty or failing fuel injectors can disrupt the air/fuel mixture enough to cause random misfires.

Diagnosis Steps

1. Check the engine oil level immediately. A very low oil level can cause the MultiAir system to function improperly, leading to misfires.
2. Scan for any other accompanying trouble codes. Codes like P0301-P0304 can help narrow the search.
3. Remove the plastic engine cover and pull out each ignition coil. Inspect the spark plug wells for any signs of liquid engine oil. If oil is present, the valve cover assembly is your primary suspect.
4. If no oil is found, remove and inspect all four spark plugs. Look for signs of wear, oil fouling, or incorrect gaps. The correct gap is 0.047 inches.
5. If you have a specific cylinder misfire code (e.g., P0302), swap that ignition coil with one from a known good cylinder (e.g., cylinder 1). Clear the codes and drive the vehicle. If the code changes to P0301, the ignition coil is faulty.
6. Check for vacuum leaks by listening for hissing sounds around the intake manifold and inspecting all vacuum hoses for cracks or loose connections. A failed PCV valve (part of the valve cover) can cause a major vacuum leak.
7. If the above steps do not reveal the cause, consider a professional diagnosis, which may include a fuel pressure test or an engine compression test to check for mechanical issues.

Parts You'll Likely Need

• Valve Cover Gasket Kit (OEM #68194324AC (or newer revisions)) — This is the most common fix for oil found in the spark plug wells, a frequent cause of P0300 on this engine. The kit includes the cover, gasket, tube seals, and integrated PCV valve.
  Trusted brands: Mopar, Fel-Pro, Mahle
  OEM price range: $80-$120
  Aftermarket price range: $50-$90
• Iridium Spark Plugs (OEM #SP148183AD (supersedes SP148183AB, SP148183AC)) — These are a primary ignition component and are often fouled by the engine's oil consumption issues or oil leaks. They are a standard replacement part for any tune-up or misfire diagnosis.
  Trusted brands: Mopar (Champion), NGK (ILKAR7B11 / 93501 or LFR5AIX-11 / 4469), Denso
  OEM price range: $15-$25 per plug
  Aftermarket price range: $10-$18 per plug
• Ignition Coil (OEM #68242286AB) — Ignition coils are a common failure point, especially when contaminated by oil from a leaking valve cover gasket.
  Trusted brands: Mopar, NGK, Delphi, Bosch
  OEM price range: $50-$80
  Aftermarket price range: $35-$70

Related Codes That Often Appear With This One

• P0301, P0302, P0303, P0304 — These codes indicate a misfire on a specific cylinder. They often accompany P0300, helping to pinpoint which cylinders are misfiring most frequently.

Technical Service Bulletins (TSBs) & Recalls

• 18-068-19 — Flash: Powertrain Control Module (PCM) Updates — For 2019 models, this TSB addresses a Malfunction Indicator Lamp (MIL) by reprogramming the PCM to correct false P0300, P0301, P0302, P0303, or P0304 misfire codes. (2019-10-10)
• 08-027-20 — Ignition Coil Insulating Boots — This TSB addresses MIL illumination for P0300-P0304 codes and involves the inspection and potential replacement of ignition coil insulating boots, particularly if they are contaminated with oil from a valve cover leak. (2020-03-04)

Platform-Specific Known Issues

• Excessive Oil Consumption: The 2.4L Tigershark engine is widely known for consuming oil. FCA has addressed this with warranty extensions (e.g., X90) and an oil consumption test procedure at dealerships. This issue is a root cause of fouled plugs and misfires.
• Leaking Valve Cover Gasket: A very common failure that allows oil to fill the spark plug tubes, directly causing ignition misfires. The PCV valve is also integrated into this cover, compounding potential issues.
• PCM Software Glitches: As noted in TSB #18-068-19, some 2019 models were prone to setting false misfire codes, requiring a software update to fix.

Mechanic-Grade Diagnostic Values

• MAP Sensor Signal Voltage (Key On, Engine Off) — expected: Approximately 4.5 - 5.0 Volts. Failure: A voltage significantly lower than this range suggests a faulty sensor or a wiring issue. This reading should correlate with the BARO sensor reading.
• MAP Sensor Signal Voltage (Engine Running at Idle) — expected: 1.0 - 2.0 Volts. Failure: Voltage that remains high (near KOEO reading) or is below 1.0V at idle indicates the sensor is not reading engine vacuum correctly.

Wiring & Ground Locations

• Primary Engine Ground Strap — A braided strap running from the transmission case to a bolt on the top of the driver's side transmission mount. It can be seen by removing the driver's side headlight.. A poor primary engine ground can cause erratic sensor readings and inconsistent ignition system performance, leading to random misfire codes.
• Ignition Coil Connector — On top of the valve cover, one for each of the four ignition coils.. This is a 2-pin connector that provides power and ground to the ignition coil. Oil contamination from a leaking valve cover gasket can foul this connector, causing a misfire.

OEM Part Supersession History

• 68242286AA → 68242286AB — Revision of the ignition coil.
• 5047980AA, 5047980AB, 5047980AC, 5047980AD → 5047980AE — Progressive revisions to the MultiAir actuator assembly ('brick').
  Heads up: Using the latest revision (AE) is recommended for repairs.

Model Year Variations Within This Range

• 2019: A specific PCM software update was released under TSB #18-068-19 to address conditions where false P0300-series misfire codes could be set. This does not apply to earlier model years.