P0302 on 2017-2022 Alfa Romeo Giulia: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2017-2022 Alfa Romeo GIULIA

For the Alfa Romeo Giulia, a P0302 code can be more than just a simple spark plug issue. 🎬 Watch: Understanding the causes of a cylinder 2 misfire. Manufacturer documents point to specific issues, including a batch of 2021-2022 vehicles built with faulty ignition coils (TSB 09-002-22), requiring all four to be replaced. Additionally, software glitches have been documented where misfire codes can appear after a PCM software update (TSB S2018000011). While standard ignition components are still the most common cause, these platform-specific issues are important to consider if a simple fix doesn't work.

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
• Difficulty starting the engine
• Unusual fuel smell from the exhaust
• Engine running rougher under load, like going uphill

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are common failure points on many modern turbocharged engines due to heat and vibration. TSB 09-002-22 specifically identifies a bad batch of coils causing misfires on Giulia and Stelvio models built between Sept 8, 2021 and Sept 28, 2021.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 1). Clear the codes and drive the car. If the code changes to P0301, the coil is faulty.
   Typical fix: Replace the faulty ignition coil. It is held down by a single 10mm bolt. If your vehicle falls under TSB 09-002-22, the dealer procedure is to replace all four coils.
   Est. part cost: $50-$90
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug The 2.0L direct-injection turbo engine has a recommended spark plug change interval of 30,000 miles, which is shorter than many vehicles. Many owners may not be aware of this, leading to misfires from worn plugs.
   How to confirm: After ruling out the coil, remove the spark plug from cylinder 2. Inspect for wear, carbon fouling, or oil. The correct gap should be between .024" and .026".
   Typical fix: Replace the spark plug. It is recommended to replace all four plugs at the same time with high-quality NGK Iridium plugs specified for the vehicle. The spark plug torque specification is 14 ft/lbs.
   Est. part cost: $80-$100 (for a set of 4)
3. Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector
   How to confirm: This is more complex to diagnose. A professional may need to perform a fuel injector flow test or use a scan tool to monitor fuel trims. Sometimes, running a high-quality fuel injector cleaner through the system can resolve minor clogs.
   Typical fix: Replace the fuel injector for cylinder 2. This is a direct-injection engine, so replacement is more involved than on a port-injected engine and may require new seals.
   Est. part cost: $120-$220
4. PCM Software Issue ⚪ Low Probability As cited in TSB S2018000011, misfire codes can be erroneously set after a specific PCM software update related to Customer Satisfaction Notification W05. Other TSBs also call for PCM updates to resolve various engine running issues.
   How to confirm: This must be confirmed by an Alfa Romeo dealership. They can check the vehicle's service history and current software version against available updates.
   Typical fix: The dealership may need to re-flash or update the Powertrain Control Module software.
   Est. part cost: $0-$250 (depending on warranty/dealer)

Rare But Worth Checking

• Low Fuel Pressure: As seen in owner complaint ODI #11597827, low fuel pressure can cause multiple cylinder misfires. This would typically be accompanied by other codes like P008A or P0087.
• Carbon Buildup on Intake Valves: Like many direct-injection (GDI) engines, the 2.0T is susceptible to carbon buildup on the back of the intake valves over time. This can disrupt airflow into the cylinder, leading to misfires, especially on cold starts. This typically requires professional cleaning (e.g., walnut blasting).
• Low Engine Compression: Internal engine issues like worn piston rings, a bad valve, or a leaking head gasket can cause a misfire that won't be fixed by replacing ignition or fuel parts. A compression test is needed to diagnose this.

Diagnosis Steps

1. Read the codes with an OBD-II scanner and note any other codes present, especially injector or fuel pressure codes.
2. To test the ignition coil, swap the coil from cylinder 2 with the coil from cylinder 1. Cylinder 1 is at the front of the engine.
3. Clear the codes and test drive the vehicle. If the code returns as P0301, the ignition coil is the problem and needs replacement.
4. If the code remains P0302, the coil is likely good. The next step is to inspect the spark plug.
5. Remove the spark plug from cylinder 2. Check for excessive wear, damage, or fouling. Ensure the gap is correct (.024"-.026").
6. If the spark plug is old or looks worn, replace it. It's best practice to replace all four at once due to the 30,000-mile service interval.
7. If the plug and coil are good, the issue may be the fuel injector. This is more difficult to test for a DIYer and may require a professional.
8. Check for any relevant TSBs or software updates with an Alfa Romeo dealer, especially if the problem started after a service or if your vehicle is a 2021-2022 model.
9. If the problem persists, consider more complex causes like a vacuum leak, fuel pressure issue, or low engine compression, which requires a compression test.

Parts You'll Likely Need

• Ignition Coil (OEM #68242286AB) — This is one of the most common failure points for a single-cylinder misfire on modern engines. TSB 09-002-22 also identified a bad batch.
  Trusted brands: Mopar, Bosch, NGK, Delphi
  OEM price range: $60-$90
  Aftermarket price range: $40-$80
• Iridium Spark Plugs (Set of 4) (OEM #NGK ILZKR7G) — The Giulia has a relatively short 30,000-mile spark plug interval, making worn plugs a frequent cause of misfires. These are the OEM-spec plugs.
  Trusted brands: NGK, Mopar
  OEM price range: $80-$100
  Aftermarket price range: $70-$90
• Fuel Injector (OEM #4893630AA) — If ignition components are ruled out, a clogged or failing fuel injector is a likely cause for a single-cylinder misfire.
  Trusted brands: Mopar, Bosch
  OEM price range: $150-$220
  Aftermarket price range: $100-$180

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or affects multiple cylinders, a P0300 (Random/Multiple Cylinder Misfire) may be stored alongside P0302.
• P0301, P0303, P0304 — These codes indicate misfires in other cylinders. If they appear together, it points to a common problem like a fuel delivery issue, vacuum leak, or a major software fault, such as the one described in TSB 09-002-22.
• P0087, P008A — These codes indicate low fuel rail or system pressure. An owner complaint (NHTSA ODI #11597827) showed these codes appearing with multiple misfire codes, suggesting a fuel pump or sensor issue was the root cause.
• P0202 — This code indicates a malfunction in the cylinder 2 injector circuit. If you see P0302 and P0202 together, it strongly points to a problem with the fuel injector for cylinder 2 or its wiring.

Technical Service Bulletins (TSBs) & Recalls

• 09-002-22: Links P030x codes on 2021-2022 models to faulty ignition coils requiring replacement of all four.
• S2018000011: Links P0302 to a specific PCM software update.

Platform-Specific Known Issues

• TSB #09-002-22 (also released as RRT 22-014): Affects some 2021-2022 Giulia and Stelvio models built between Sept 8 and Sept 28, 2021. A manufacturing issue with a 'double wire' in the ignition coils can cause misfires (P0301, P0302, P0303, P0304). The fix is to replace all four ignition coils.
• TSB #S2018000011 warns that P0302 and other misfire codes can be triggered by a PCM software update for Customer Satisfaction Notification (CSN) W05.
• Owner complaint NHTSA ODI #11597827 reported multiple misfire codes, including P0302, along with low-pressure fuel system codes (P008A, P0087), indicating a fuel delivery problem as the root cause.

Mechanic-Grade Diagnostic Values

• Spark Plug Torque — expected: 14 ft/lbs (19 Nm). Failure: N/A (Installation specification)
• High-Pressure Fuel Injection System — expected: Up to 2,900 psi (200 bar). Failure: Significantly lower pressure under load would indicate a high-pressure fuel pump issue.

Hidden / Shadow Codes Worth Checking

• Mode 6 Misfire Counters: The Engine Control Module (ECM) tracks misfire events per cylinder over the current and previous driving cycles. These counters can show a cylinder is misfiring before the count is high enough to trigger a P0302 trouble code and check engine light. (see via A professional scan tool capable of displaying Mode 6 test results. Some tools, like the one shown in a diagnostic video, automatically decode the Test IDs (e.g., TID $A2) into readable descriptions.)

Scan Tool Commands That Help

• Autel/Professional Scan Tool: Misfire Data Stream / Oscilloscope — Technicians have noted that the standard live data stream on some scan tools may not include misfire counter PIDs for the Giulia. If live misfire data is not available, a technician may need to use an oscilloscope to analyze the ignition coil and fuel injector waveforms for cylinder 2 to identify the fault.
• MultiECUScan: Parameter Monitoring & Actuator Tests — This is a highly regarded third-party diagnostic software for Fiat-Chrysler-Alfa Romeo vehicles. It can be used to monitor detailed engine parameters beyond standard OBD-II, including those related to the MultiAir system, and perform actuator tests that may help diagnose a persistent misfire.

Wiring & Ground Locations

• Engine/Transmission Ground Strap — Under the vehicle, connecting the transmission to the chassis. It is often left exposed to the elements.. This main ground strap is known to corrode and fail, leading to a no-start condition or severe electrical issues. A poor ground can cause insufficient voltage for the ignition coils to fire properly, potentially leading to misfires. If a no-start occurs, the starter motor may attempt to ground through smaller wires, melting them.
• Remote Negative (-) Jump-Start Post — An exposed metal stud on the upper frame rail in the engine bay, near the passenger side hood lock.. This is the primary, manufacturer-designated ground point in the engine bay for testing or jump-starting. When checking for voltage drop or testing the ground circuit for the cylinder 2 coil or injector, this is the correct reference point to use.
• Remote Positive (+) Jump-Start Post — Under a red protective flap, located at the rear of the engine compartment (Non-Quadrifoglio models).. This is the main power distribution point in the engine bay. It can be used as a reference point for testing voltage supplied to the ignition coils and fuel injectors.

Real Owner Repair Stories

• Reddit user on r/AlfaRomeo (2017 Giulia Ti, ~44k miles) — No codes or symptoms were present. This was a preventative maintenance job based on the manufacturer's recommended 30,000-mile spark plug interval.
  ✅ What actually fixed it The user preventatively replaced all four original spark plugs and ignition coils. The post documents the process, tools, and part sources, confirming the job was straightforward and the car continued to run beautifully afterward. The user noted the spark plug torque value is 14 ft/lbs.

OEM Part Supersession History

• 68080580AB, 68242286AA → 68242286AB — Standard part revision and consolidation by the manufacturer.

Model Year Variations Within This Range

• 2017-2018: Anecdotal reports from owners and mechanics suggest that the MultiAir valvetrain units on earlier models may be more prone to failure. An improved or revised part is believed to have been used in engines from the 2019 model year onward.
• 2021-2022 (specific build dates): As noted in TSB 09-002-22, a specific batch of vehicles built between September 8, 2021, and September 28, 2021, were fitted with defective ignition coils from the factory, requiring all four to be replaced.