P0301 on 2016-2018 Fiat 500X: Cylinder 1 Misfire Causes and Fixes

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

The 2016-2018 Fiat 500X was available with two distinct engines: the 1.4L MultiAir Turbo and the 2.4L Tigershark MultiAir2. Both use Fiat's MultiAir technology, which relies on engine oil pressure to control the intake valves. This makes them uniquely sensitive to oil level and quality; low or dirty oil can cause misfires that might be mistaken for ignition or fuel system faults. 🎬 Watch: Diagnosing misfire codes on the Fiat 500X engine. The 2.4L Tigershark engine, in particular, is known for issues with oil consumption and has a specific Technical Service Bulletin (TSB #08-027-20) addressing misfire codes by replacing just the ignition coil boots, indicating a common failure point in the seal. Furthermore, the valve cover gasket on the 2.4L is a frequent failure point, allowing oil to leak into the spark plug tubes and saturate the ignition coils, causing misfires.

Diagnostic Flowchart

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

Symptoms You May Notice

• Flashing or solid Check Engine Light
• Rough or shaky idle
• Engine hesitation or stumbling during acceleration
• Noticeable loss of power
• Reduced fuel economy
• Smell of unburnt gasoline from the exhaust
• Car may enter 'limp mode' with reduced power.

Most Likely Causes

1. Failed Ignition Coil or Boot 🔴 High Probability For the 2.4L engine, FCA issued TSB #08-027-20 specifically to address misfires (P0300-P0304) by replacing the ignition coil boots, which can degrade, swell, or fail to seal properly. Oil leaks from the valve cover gasket can also saturate and destroy the coil and boot, a very common occurrence on the 2.4L Tigershark.
   How to confirm: Swap the ignition coil from cylinder 1 with another cylinder (e.g., cylinder 2). Clear the codes and drive. If the code changes to P0302, the ignition coil is the faulty part. Visually inspect the coil and boot for cracks, swelling, or oil contamination. Oil in the spark plug well is a clear sign of a leaking valve cover gasket and the likely cause of the coil failure.
   Typical fix: Replace the faulty ignition coil and spark plug. For the 2.4L, per TSB 08-027-20, you may only need to replace the coil boot and spring with new parts and apply the specified dielectric grease. It is best practice to replace all coils and plugs at the same time. If oil was present, the valve cover gasket and tube seals must be replaced to prevent a repeat failure.
   Est. part cost: $40-$90 per coil
2. Worn or Fouled Spark Plug 🔴 High Probability Spark plugs are a standard wear item. On the 2.4L engine, which is known for oil consumption, plugs can become fouled with oil, leading to a weak or non-existent spark. The 1.4L Turbo has a shorter service interval for plugs (approx. 30,000 miles). Incorrectly gapped plugs are also a common issue after a tune-up. The specified gap for the 1.4L is around 0.027" while the 2.4L is around 0.044"-0.047".
   How to confirm: Remove the spark plug from cylinder 1. Inspect the electrode for excessive wear, carbon buildup, or oil fouling. Compare it to a new plug. Check the gap with a feeler gauge.
   Typical fix: Replace the spark plug in cylinder 1. It is highly recommended to replace all spark plugs as a set to ensure consistent performance. Ensure new plugs are gapped correctly for your specific engine.
   Est. part cost: $10-$25 per spark plug
3. Low or Dirty Engine Oil 🟡 Medium Probability Both the 1.4L and 2.4L engines use the MultiAir system, which uses engine oil to hydraulically actuate the intake valves. If the oil level is low or the oil is dirty/incorrect viscosity, it can starve the MultiAir actuator ('brick'), causing valve timing issues and misfires that mimic ignition problems. The 2.4L Tigershark's known oil consumption issue makes this a critical first check. There are many forum reports of misfire codes being resolved simply by an oil change or top-off, as was the case for one Fiat 500 owner.
   How to confirm: Check the engine oil level and condition using the dipstick. If the level is low, top it off with the manufacturer-specified oil type and see if the misfire improves. Note the date of the last oil change. This should be the very first step in diagnosing a misfire on these engines.
   Typical fix: Perform an oil and filter change using the correct specification oil (e.g., Mopar-approved full synthetic). If the issue persists after confirming oil level and quality, the MultiAir actuator itself may be failing.
   Est. part cost: $50-$100 for oil and filter

Rare But Worth Checking

• Faulty Fuel Injector: A clogged or failing fuel injector can prevent the correct amount of fuel from entering cylinder 1. This is less common than ignition issues but should be considered if spark components are good.
• MultiAir Actuator ('Brick') Failure: On the 1.4L engine especially, the entire MultiAir actuator assembly can fail, often causing multiple misfires (P0300) but sometimes starting with a single cylinder (P0301) and other codes like P106B. This is an expensive and complex repair, often costing over $2,000-$3,000 at a dealership.
• Low Engine Compression: A mechanical engine problem, such as a leaking valve or worn piston rings, can cause a loss of compression in cylinder 1. This is a serious issue requiring a compression test to diagnose and likely involves significant engine repair.
• Failed PCV Valve: A faulty Positive Crankcase Ventilation (PCV) valve can cause a variety of issues including rough running, hesitation, and oil consumption, potentially leading to misfire codes. One owner of a 2016 500X 1.4L reported that replacing a broken PCV valve resolved long-standing issues with hesitation and a smell of petrol.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0301 and check for any other pending or active codes.
2. CRITICAL FIRST STEP: Check the engine oil level and condition. Top up or change if necessary, using the manufacturer-specified oil. Many misfires on this platform are resolved at this step.
3. Visually inspect the wiring and connector for the cylinder 1 ignition coil for any damage or loose connections.
4. Remove the cylinder 1 ignition coil. Inspect the spark plug well for any signs of oil. Oil presence indicates a failed valve cover gasket that must be replaced.
5. Swap the ignition coil from cylinder 1 to cylinder 2. Clear the codes, run the engine, and see if the misfire code moves to P0302. If it does, the coil is bad.
6. If the coil is not the issue, remove the spark plug from cylinder 1. Inspect it for wear, damage, or oil fouling. Check the gap. If it's in poor condition, replace all spark plugs, ensuring correct gap.
7. If spark components are good, check for a clogged or faulty fuel injector. You can listen for a clicking sound from the injector with a mechanic's stethoscope or swap it with another cylinder (more advanced).
8. If the problem persists, perform an engine compression test to check for mechanical issues within cylinder 1.

Parts You'll Likely Need

• Ignition Coil (OEM #68242286AB (supersedes 68242286AA)) — This is a primary failure point for misfires on this platform, especially on the 2.4L engine when contaminated by oil.
  Trusted brands: Mopar, Bosch, NGK
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plug (2.4L Tigershark) (OEM #Mopar SP148183AB / NGK LZFR5C-11) — A standard maintenance item that is often the direct cause of a misfire due to wear or oil fouling from a leaking valve cover gasket.
  Trusted brands: NGK, Champion, Denso
  OEM price range: $15-$25
  Aftermarket price range: $8-$20
• Spark Plug (1.4L MultiAir Turbo) (OEM #Mopar SP070507AC / NGK SIKR9A7) — A standard maintenance item with a relatively short service life (30k miles) that can cause misfires when worn.
  Trusted brands: NGK, Denso
  OEM price range: $20-$30
  Aftermarket price range: $15-$25
• Ignition Coil Boot — For the 2.4L engine, TSB #08-027-20 identifies the boot itself as a common failure point that can be replaced separately from the coil.
  Trusted brands: Mopar
  OEM price range: $10-$20

Related Codes That Often Appear With This One

• P0300 — This code for 'Random/Multiple Cylinder Misfire' often appears alongside P0301 if the underlying issue, like a vacuum leak, low oil level, or failing MultiAir actuator, begins to affect other cylinders.
• P0302, P0303, P0304 — If other cylinder-specific misfire codes are present, it points towards a systemic problem like a failing MultiAir actuator, low fuel pressure, or a major vacuum leak.
• P0106 — This code for 'Manifold Absolute Pressure (MAP) Sensor Range/Performance' can appear with misfire codes, as a misfire can cause erratic pressure readings in the intake manifold. A Fiat 500X owner reported this code appearing alongside multiple misfire codes.

Technical Service Bulletins (TSBs) & Recalls

• 08-027-20: Addresses P0301 and other misfire codes on the 2.4L engine by recommending the replacement of all four ignition coil insulating boots. [Bulletin #08-027-20]

Platform-Specific Known Issues

• TSB #08-027-20: For the 2.4L engine, FCA issued a bulletin for replacing all four ignition coil insulating boots to resolve misfire codes, including P0301. This suggests the boots are a known weak point.
• 2.4L Tigershark Oil Consumption: These engines are known to consume excessive amounts of oil between changes. This can lead to low oil levels, which compromises the MultiAir system and can cause misfires. This should be the first thing checked.
• 2.4L Valve Cover Gasket Leaks: The valve cover gasket and integrated spark plug tube seals frequently fail, allowing oil to pool in the spark plug wells, which saturates and destroys the ignition coils and plugs, causing misfires.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance (2.4L) — expected: While no exact OEM value is published, all four injectors should have resistance values very close to each other.. Failure: An injector with a significantly higher or lower resistance reading, or an open circuit (infinite resistance), is considered faulty.

Scan Tool Commands That Help

• Multi-Ecu-Scan (MES) / AlfaOBD: Phonic Wheel Relearn — This procedure may be required after major engine work, such as replacing a timing belt or the engine itself. Failure to perform the relearn can cause random misfire codes to appear during low-load cruising, even when no actual misfire is occurring.

Wiring & Ground Locations

• Engine Ground Wires — General engine bay area, connected to the engine block/head and chassis.. A loose or corroded ground wire for the engine can cause a variety of electrical issues, including weak spark, which can lead to misfire codes like P0301. It's a crucial check if ignition components seem to be in good order.

Real Owner Repair Stories

• The FIAT Forum user 'Dion500X' (2016 Fiat 500X 1.4L MultiAir) — Smell of petrol and engine oil in the cabin on warm starts, car was slow and laggy, almost cutting out in first and second gear.
  ❌ Tried (didn't work) The user was dealing with the issue since 'almost day one' of owning the car.
  ✅ What actually fixed it The user discovered the PCV valve was broken. Replacing the PCV valve transformed the car, making it pull smoothly and effortlessly.
• YouTube user 'P0301 on Cherokee KL 4 Cylinder' (2016 Jeep Cherokee 2.4L (same engine family), 75,000 miles) — Hesitation and hiccuping, P0301 code.
  ❌ Tried (didn't work) Replacing the spark plug in cylinder 1.
  ✅ What actually fixed it Replacing the ignition coil in cylinder 1 solved the problem.

OEM Part Supersession History

• 68242286AA, 68080580AB → 68242286AB — Standard part revision and consolidation by the manufacturer.
  Heads up: The new part number 68242286AB is the correct replacement for the older numbers on the 2.4L engine.
• Standard Fiat 1.4L Turbo Coils → Alfa Romeo 4C Ignition Coils — Performance Upgrade
  Heads up: Genuine ignition coils from the Alfa Romeo 4C are a direct-fit, bolt-in performance upgrade for the 1.4L MultiAir Turbo engine in the Fiat 500X. They are recommended for vehicles with ECU tunes to help reduce misfires at high RPM.

Model Year Variations Within This Range

• 2016-2018: The 2018 model year introduced the Uconnect 4 system with Apple CarPlay and Android Auto as standard, which was a change from previous years. However, the core powertrain options (1.4L Turbo and 2.4L Tigershark) and their common P0301 causes remained the same across this range.
• Post-2018 (2019+): For the 2019 model year, Fiat significantly changed the 500X, discontinuing both the 1.4L and 2.4L engines and replacing them with a new 1.3L MultiAir III turbo engine. All-wheel drive became standard. Therefore, information specific to the 2016-2018 engines does not apply to 2019 and newer models.