P0302 on 2016-2018 Fiat 500X: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2016-2018 Fiat 500X

The Fiat 500X from this period uses two main engines, the 1.4L Turbo and the 2.4L 'Tigershark', both featuring Fiat's MultiAir electro-hydraulic valve control system. While standard ignition components like coils and plugs are the most common culprits for a P0302, these engines have specific, well-documented issues. The 2.4L Tigershark is notorious for a valve cover gasket that leaks oil into the spark plug tubes, fouling the plug and coil. Both engines are also sensitive to oil quality and level, as dirty, low, or incorrect oil can affect the MultiAir system and potentially lead to misfires, a point corroborated by owner experiences on forums.

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 shaky idle.
• Flashing or solid Check Engine Light.
• Noticeable loss of power and acceleration.
• Engine hesitation or stumbling.
• Difficulty starting the engine.
• Reduced fuel economy.
• Unusual odor from the exhaust.

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Ignition coils are a common wear item. On the 2.4L engine, oil leaking from the valve cover gasket can saturate the coil boot, causing it to swell, degrade, and fail. TSB 08-027-20 was issued specifically to address misfires on the 2.4L engine by replacing just the insulating boots, highlighting this as a known failure point.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 1). Clear the codes and drive. If the code changes to P0301, the ignition coil is the faulty part. Visually inspect the coil boot for oil saturation, swelling, or cracks.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace the corresponding spark plug at the same time. If oil was present, the valve cover gasket must also be replaced.
   Est. part cost: $40 - $115
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a routine maintenance item. On the 2.4L engine, a common valve cover gasket leak can foul the spark plugs with oil, causing a misfire. The 2.4L Tigershark is also known for excessive oil consumption, which can foul plugs from within the cylinder.
   How to confirm: After ruling out the ignition coil, remove the spark plug from cylinder 2. Inspect it for wear (worn electrode), carbon deposits, or oil contamination on the threads or electrode.
   Typical fix: Replace the spark plug. If oil is present in the spark plug tube, the valve cover gasket must also be replaced to prevent a repeat failure. Ensure the new plug is gapped correctly.
   Est. part cost: $15 - $25 per plug
3. Leaking Valve Cover Gasket (2.4L Engine) 🟡 Medium Probability → Shop Engine Valve Cover This is a widely documented issue on the 2.4L Tigershark engine across multiple FCA platforms (Jeep, Dodge, Chrysler). 🎬 Watch: Common causes for misfires on the 2.4L engine. The gasket's integrated spark plug tube seals degrade, allowing engine oil to flood the spark plug wells, shorting out the coil and plug.
   How to confirm: When you remove the ignition coil from cylinder 2, you will see visible liquid engine oil on the coil boot and down in the spark plug tube. You may also smell burning oil from the engine bay.
   Typical fix: Replace the valve cover gasket and the spark plug tube seals (they typically come in a kit). Thoroughly clean the oil from the spark plug tube and replace the oil-fouled spark plug and ignition coil boot/assembly.
   Est. part cost: $25 - $40 for a gasket kit
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: If swapping the coil and plug doesn't resolve the issue, the fuel injector is a possible cause. A more advanced diagnostic is to swap the fuel injector from cylinder 2 with another cylinder, though this is more labor-intensive. A mechanic can also perform a resistance check or flow test.
   Typical fix: Replace the fuel injector for cylinder 2.
   Est. part cost: $100 - $500

Rare But Worth Checking

• MultiAir System Fault: The MultiAir system is hydraulically actuated by engine oil. Low or dirty oil can cause issues. In some cases, a failure of the MultiAir 'brick' or its solenoids can cause a persistent misfire on a single cylinder. This is a known issue on platform mates like the Dodge Dart and is often accompanied by codes like P1067 (Cylinder 2 Oil Supply Solenoid Valve).
• Low Engine Compression: Internal engine damage such as a burnt valve, worn piston rings, or a failed head gasket can cause a loss of compression, leading to a misfire. A Reddit user with a Fiat 500L reported a P0302 with a no-compression finding from their mechanic, requiring an engine replacement.
• Low or Incorrect Engine Oil: A thread on The FIAT Forum regarding a 500X with P0300 and P0302 codes revealed the ultimate cause was a completely dry dipstick. Topping up the oil resolved the misfire. The MultiAir system is highly sensitive to oil level and quality.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0302 and check for any other codes.
2. Identify cylinder 2. On the inline-four engines in the 500X, the cylinders are numbered 1-2-3-4, starting from the timing belt/pulley side (passenger side in the US) and counting towards the transmission (driver's side).
3. CHECK THE OIL. Before any other steps, verify the engine oil is at the correct level and in good condition. Low oil has been confirmed by owners to cause this code.
4. Swap the ignition coil from cylinder 2 with the coil from cylinder 1. Clear the codes and run the engine to see if the misfire moves. If the scanner now shows a P0301 code, the ignition coil is bad and needs replacement.
5. If the code remains P0302, inspect the spark plug tube for any signs of oil while the coil is out. If oil is present, the valve cover gasket and tube seals need to be replaced.
6. If no oil is found, swap the spark plug from cylinder 2 with the one from cylinder 1. If the code changes to P0301, the spark plug is faulty.
🎬 Watch: How to diagnose and fix a P0302 misfire code.
7. If the misfire persists on cylinder 2 after swapping the coil and plug, the issue may be with the fuel injector or a mechanical problem.
8. Consider having a professional test the fuel injector's function or perform a compression test on cylinder 2 to check for mechanical engine problems like worn rings or a bad valve.

Parts You'll Likely Need

• Ignition Coil (OEM #68242286AB (2.4L), 68081914AC (1.4L)) — This is one of the most common failure points for a single-cylinder misfire, especially when exposed to oil from a leaking gasket on the 2.4L engine.
  Trusted brands: Mopar, Bosch, NGK, Denso
  OEM price range: $70-$115
  Aftermarket price range: $40-$90
• Spark Plug (OEM #NGK LZFR5C-11 (2.4L), NGK SIKR9A7 (1.4L)) — Spark plugs are a routine maintenance part and can become worn or fouled, especially by oil from a leaking valve cover gasket on the 2.4L engine.
  Trusted brands: Mopar, NGK, Champion
  OEM price range: $20-$25
  Aftermarket price range: $15-$20
• Valve Cover Gasket Kit (2.4L) (OEM #68194923AB) — Required to fix the common oil leak into the spark plug tubes on the 2.4L Tigershark engine, which is a primary cause of P0302. The original part number 05047440AC has been superseded.
  Trusted brands: Mopar, Fel-Pro, Mahle
  OEM price range: $25-$40
  Aftermarket price range: $20-$35

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or begins to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) may be set. This can happen if the root cause is systemic, like low oil level or a vacuum leak.
• P0301, P0303, P0304 — If the cause of the misfire is systemic (e.g., bad fuel, a large vacuum leak, or a failing MultiAir unit), codes for other cylinders may appear alongside P0302. On the 2.4L, multiple misfire codes often point to a valve cover gasket that is leaking into multiple spark plug tubes.
• P1067 — This manufacturer-specific code points to a fault with the Cylinder 2 Oil Supply Solenoid Valve within the MultiAir system, directly linking the misfire to a potential MultiAir actuator issue. This is a known issue on platform mates.

Technical Service Bulletins (TSBs) & Recalls

• 08-027-20: Addresses rough running and MIL illumination for codes P0300, P0301, P0302, P0303, and P0304 on 2.4L engines, involving the replacement of ignition coil boots.

Platform-Specific Known Issues

• TSB 08-027-20: Fiat Chrysler Automobiles (FCA) issued this Technical Service Bulletin for the 2.4L engine due to misfire codes (P0300-P0304). The bulletin addresses rough running conditions and involves replacing all four ignition

Mechanic-Grade Diagnostic Values

• Ignition Coil Resistance (2.4L Engine) — expected: Primary: 0.56 - 0.68 Ohms. Secondary: 7.8 - 9.6 kOhms.. Failure: Readings outside of this range indicate a faulty coil.
• Fuel Injector Resistance — expected: All injectors should have very similar resistance values.. Failure: An injector that has no reading (open circuit) or a reading that is significantly different from the others is likely faulty.
• High Pressure Fuel Rail (1.4L Turbo Engine) — expected: Can reach up to 2000 bar (29,000 PSI).. Failure: Significantly lower pressure under load would indicate a problem with the high-pressure fuel pump.

Hidden / Shadow Codes Worth Checking

• Misfire Counters (per cylinder): Beyond the single P0302 code, advanced scan tools can access counters that track the number of misfire events per cylinder over current and previous drive cycles. This helps determine if the fault is intermittent, worsening, or historical. (see via Using an advanced, FCA-compatible scan tool like AlfaOBD or the dealer wiTECH tool.)

Scan Tool Commands That Help

• wiTECH (Dealer Tool): Active Test: Cylinder 1-4 Oil Supply Solenoid Valve — If a MultiAir system fault is suspected (e.g., if code P1067 is also present), this command individually actuates the solenoid for cylinder 2. The technician should listen for an audible click. No click suggests a failed solenoid within the MultiAir 'brick'.
• wiTECH (Dealer Tool): MultiAir Lube Oil System Purge — This service procedure should be run after replacing the MultiAir actuator or after an instance of the engine oil running critically low. It helps purge air from the hydraulic actuation system.
• AlfaOBD: Active Diagnostics — This software provides many dealer-level functions for owners, including the ability to run active tests on components like fuel injectors and solenoids to help pinpoint the cause of the misfire without swapping parts.

Wiring & Ground Locations

• Engine Wiring Diagrams — Vehicle-specific, routed throughout the engine bay.. A chafed or broken wire leading to the cylinder 2 ignition coil or fuel injector will cause a persistent P0302. Access to a wiring diagram is necessary to trace the circuit from the PCM to the component to check for continuity and shorts. A forum thread on fiat500owners.com reportedly contains several wiring diagram PDFs for the 2016 2.4L model.
• Engine Ground Point — The owner's manual specifies a dedicated ground point on the engine block for jump-starting, away from the battery.. While specified for jump-starting, this indicates a solid, accessible ground connection. A poor engine ground can cause numerous electrical issues, including weak spark and misfires. Verifying all main engine-to-chassis ground straps are clean and tight is a valid diagnostic step.

Real Owner Repair Stories

• The FIAT Forum user 'Dion500X' (2016 Fiat 500X with 1.4L MultiAir engine) — Ugly smell of petrol and engine oil in the cabin on warm starts, car was slow, laggy, and almost cutting out in 1st and 2nd gear.
  ❌ Tried (didn't work) The user did not specify things tried, but was driven 'crazy' by the problem before finding the solution.
  ✅ What actually fixed it Replacing a broken PCV (Positive Crankcase Ventilation) valve. The user noted that after replacement, the fuel smell was gone and the car pulled better. Another user in the same thread confirmed the fix worked for them as well.

"I Checked Everything" — The Actual Cause

• A persistent misfire or misfire-like symptoms (hesitation, rough running) with no obvious vacuum leaks from a smoke test could be caused by a faulty PCV valve. If the valve itself is stuck internally or the plastic housing is cracked, it can create a vacuum leak that is hard to trace, leading to an incorrect air-fuel mixture and symptoms that mimic a misfire.

When the Usual Fixes Don't Work

• While the most common causes for P0302 are ignition-related, owner reports confirm that other systems can be the root cause. In one documented case for a 2016 1.4L 500X, persistent hesitation and a fuel smell that presented like a misfire were ultimately fixed by replacing the PCV valve, not the spark plug or ignition coil. This highlights the importance of checking the crankcase ventilation system if the primary ignition and fuel components check out.

OEM Part Supersession History

• 68242286AA → 68242286AB — Standard part revision by the manufacturer.
  Heads up: The parts are interchangeable, with 'AB' being a later, likely improved, version of 'AA'.
• 05047440AC → 68194923AB — Part was updated by the manufacturer, likely to address the known leaking issue.

Model Year Variations Within This Range

• 2018: The 2018 model year received a new standard Uconnect 4 infotainment system with a 7-inch touchscreen, which included Apple CarPlay and Android Auto capability. This does not affect the diagnosis of P0302 but is a key difference from the 2016-2017 models.