P0302 on 2012-2019 Jeep Wrangler: Cylinder 2 Misfire Causes & Fixes

What's Unique About the 2012-2019 Jeep WRANGLER

For the 3.6L Pentastar V6 engine in this Wrangler generation, P0302 is an infamous code. It is frequently a symptom of a significant mechanical failure rather than a simple ignition problem. Early models (especially those built before July 25, 2012) were particularly prone to a manufacturing defect in the left-side cylinder head, which houses cylinders #2, #4, and #6. This issue, typically a worn valve seat, was so widespread that it prompted a manufacturer warranty extension (X56) for 10 years or 150,000 miles. Later models can still suffer from related valvetrain problems like failed rocker arms with worn bearings, making this code a high-priority for diagnosis across all model years.

Diagnostic Flowchart

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

Generation note: The 2012-2019 range covers the end of the Wrangler JK generation (2012-2018) and the beginning of the JL generation (2018-2019). Both primarily used versions of the 3.6L Pentastar V6. The most severe issue, the cylinder head failure, is most documented in the 2012-2013 JK models under warranty extension X56. However, valvetrain issues like rocker arm failure and other causes can affect all years in this range, with owners of 2016, and 2017 models also reporting the code leading to major repairs. The 2018 model year is a split; the Wrangler JK continued with the original 3.6L Pentastar, while the all-new 2018 Wrangler JL introduced an upgraded version of the 3.6L engine.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough idle or engine vibration, sometimes only when in park or at a stop light
• Engine hesitation or stumbling during acceleration
• Noticeable loss of power
• Engine stalling
• Audible ticking or tapping sound from the driver's side of the engine, which is a strong indicator of a rocker arm/lifter issue
• Decreased fuel economy

Most Likely Causes

1. Cracked or Defective Left Cylinder Head 🔴 High Probability Early 3.6L Pentastar engines (2011-2013 models) had a known manufacturing defect causing excessive wear on the valve seats of the left cylinder head, which includes cylinder #2. This was the subject of TSB #09-002-14 and warranty extension X56, which covered the repair for 10 years/150,000 miles. Even on later models, this remains a possible, though less frequent, cause.
   How to confirm: A compression test will show low pressure in cylinder #2 (one owner reported 80psi). 🎬 Watch: Diagnosing low compression and misfire on a 2016 Wrangler. A cylinder leak-down test is the definitive diagnostic step; per TSB #09-002-14, leakage of 25% or more confirms the diagnosis.
   Typical fix: Replacement of the left cylinder head assembly with the updated part. This is a major repair that also requires replacing gaskets for the valve cover, intake, and exhaust.
   Est. part cost: $800-$1500
2. Failed Rocker Arm and/or Lifter 🟡 Medium Probability The Pentastar valvetrain is known for issues with rocker arm bearings failing. The needle bearings can disintegrate, causing the roller to develop flat spots, which results in a ticking noise and prevents the valve from opening completely, leading to a misfire. An owner of a 2016 model with 50k miles reported this exact failure causing a P0302 code.
   How to confirm: Listen for a distinct ticking sound from the upper driver's side of the engine. Diagnosis requires removing the valve cover for visual inspection of the rocker arms and camshaft lobes for wear or damage. A broken rocker arm can cause low compression and a misfire even without making noise.
   Typical fix: Replacement of all rocker arms and lifters on the affected cylinder bank (driver's side). It is critical to inspect the camshaft lobes for scoring or damage, as metal debris from the failed rocker can ruin the cam, necessitating a more expensive repair. 🎬 See this walkthrough for replacing rocker arms, lifters, and camshafts.
   Est. part cost: $150-$400
3. Worn or Fouled Spark Plug 🟡 Medium Probability Spark plugs are a standard maintenance item. While not a platform-specific flaw, it's a common cause for any misfire code and should be inspected. However, due to the more serious known issues with the Pentastar, it's often a misdiagnosis. An owner complaint noted that replacing spark plugs did not solve their P0302 issue, pointing to a deeper problem.
   How to confirm: Remove the spark plug from cylinder #2 and inspect it for wear, carbon fouling, or oil/coolant contamination.
   Typical fix: Replace the spark plug. It is recommended to replace all six at the same time, along with the upper and lower intake plenum gaskets which must be removed for access.
   Est. part cost: $5-$20 per plug
4. Faulty Ignition Coil ⚪ Low Probability Ignition coils can fail over time. While possible, it's less likely to be the root cause on this engine compared to the mechanical issues above. Many owners replace the coil with no resolution.
   How to confirm: Swap the ignition coil from cylinder #2 with another cylinder on the same bank (e.g., cylinder #4). Clear the codes and drive the vehicle. If the code changes to P0304, the coil is bad. This is a simple and free diagnostic step.
   Typical fix: Replace the faulty ignition coil.
   Est. part cost: $30-$75

Rare But Worth Checking

• Faulty Fuel Injector: A clogged or failing fuel injector can cause a lean misfire. This can sometimes be resolved with a quality fuel system cleaner or a professional injector cleaning service, but may require replacement. Some owners have replaced the injector only to have the code return, indicating a different root cause.
• Wiring Harness Issue: The wiring harness for the ignition coils and injectors can become chafed or damaged, causing an intermittent short or open circuit. Visually inspect the harness, especially where it might rub against the engine or other components. One owner reported a poorly seated pin in a wiring harness connector caused an intermittent P0302.
• Leaking Head Gasket: An owner of a 2018 model reported needing regular antifreeze top-offs along with a P0302 code, which was ultimately diagnosed as a bad head gasket. This allows coolant to enter the cylinder, fouling the spark and causing a misfire, which can also damage O2 sensors.
🎬 Watch: Complete 3.6L engine rebuild including head gaskets and timing.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0302 and check for any other codes like P0300, P0304, or P0306.
2. Listen for a distinct ticking or tapping noise from the driver's side of the engine. A clear tick is a strong clue pointing towards a rocker arm/lifter failure.
3. Crucial Step: Mechanical Health Check. Perform a cylinder compression test on cylinder #2. A significantly lower reading (e.g., 80-100 psi when others are 150+) points towards a mechanical problem.
4. If compression is low, perform a cylinder leak-down test. Per TSB #09-002-14, leakage of 25% or more confirms a faulty cylinder head, likely from a bad valve seat.
5. If compression and leak-down tests are good, proceed with standard misfire diagnosis.
6. Swap the ignition coil from cylinder #2 with cylinder #4 (the middle cylinder on the same driver's side bank). Clear codes. If the code returns as P0304, the coil is faulty.
7. If the code does not move, inspect the spark plug from cylinder #2. Look for excessive wear, oil, or coolant fouling.
8. If the plug and coil are good, the issue may be with the fuel injector or wiring. Consider running a high-quality fuel injector cleaner.
9. If ticking is present but compression is good, the most likely cause is a failing rocker arm. This requires removing the valve cover for inspection.

Parts You'll Likely Need

• Left Cylinder Head Assembly (OEM #RL141353AC) — This is the most common and severe cause of a P0302 on 2012-2013 models due to a factory defect. This is the updated part number for the redesigned head specified in TSB 09-002-14.
  Trusted brands: Mopar
  OEM price range: $1000-$1500
  Aftermarket price range: $800-$1200
• Rocker Arm & Lifter Kit (OEM #5184296AH (Rocker Arm), 5184332AA (Lifter/Tappet)) — A known failure point in the Pentastar valvetrain that can cause ticking and misfires. The rocker arm part number has been superseded multiple times (from AD, AE, AF, AG to AH). It's recommended to replace all 12 on one head at once.
  Trusted brands: Mopar, Mahle, Sealed Power
  OEM price range: $250-$400 for a full set for one head
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• P0300 — If the misfire is severe or intermittent, the computer may also log a P0300 (Random/Multiple Misfire) code, especially if the underlying valvetrain issue is beginning to affect other cylinders.
• P0304 / P0306 — Because the primary issue is often the entire left cylinder head, it's common to see misfire codes for the other cylinders on that bank (4 and 6) appear alongside P0302. The TSB for the cylinder head specifically lists these three codes together.

Technical Service Bulletins (TSBs) & Recalls

• TSB #09-002-14 Rev. B (December 15, 2014): This is the key document outlining the diagnosis and repair for the defective left cylinder head on 2011-2013 3.6L engines. It specifically lists DTCs P0300, P0302, P0304, and P0306 and instructs technicians to perform a leak-down test. If leakage is 25% or greater, the left cylinder head is to be replaced under the X56 warranty extension.
• Warranty Bulletin D-14-12 (June 10, 2014): This bulletin officially announced the X56 Extended Warranty, covering the 3.6L left cylinder head for 10 years or 150,000 miles for a list of Chrysler/Dodge/Jeep vehicles, including the 2012-2013 Wrangler.

Platform-Specific Known Issues

• Warranty Extension X56: For 2011-2013 models (including the 2012-2013 Wrangler), Chrysler issued a 10-year, 150,000-mile warranty for the left cylinder head to address this specific P0302/P0304/P0306 issue. While this warranty has likely expired for most vehicles due to the 10-year time limit, its existence confirms the severity and prevalence of the defect.
• Rocker Arm Ticking: The 'Pentastar tick' is a widely discussed issue. It's caused by the failure of needle bearings in the rocker arms. On the Wrangler, a P0302 accompanied by a ticking sound from the driver's side of the engine almost certainly points to this as the cause, especially on models from 2014 onwards.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: 0.46 - 0.57 Ohms. Failure: A reading significantly outside this range indicates a faulty coil.
• Ignition Coil Secondary Resistance — expected: 6,000 - 15,700 Ohms (6kΩ - 15.7kΩ). Failure: A reading outside this range suggests the coil's internal windings are compromised.
• Ignition Coil Connector Voltage (Key On, Engine Off) — expected: Approximately 12V (Battery Voltage) at the power feed pin.. Failure: Low or no voltage points to a wiring or PCM driver issue, not a bad coil.
• Mode 6 Misfire Count (Cylinder 2) — expected: 0 or a very low number.. Failure: A high count for cylinder 2, even without a current CEL, confirms an intermittent misfire is occurring. The maximum value displayed is often 65535, which is a data limit, not an actual count.

Scan Tool Commands That Help

• wiTECH or equivalent professional scan tool: Cylinder Power Balance Test / Injector Kill Test — This is a crucial diagnostic step when a misfire is felt at idle but the cause isn't obvious. The test deactivates one cylinder at a time (by cutting fuel) and measures the corresponding drop in RPM. If disabling cylinder #2 causes little or no RPM drop compared to other cylinders, it confirms cylinder #2 is not contributing power, isolating the fault.

Wiring & Ground Locations

• Cylinder #2 Ignition Coil Connector — Driver's side of the engine, front-most coil (closest to the radiator). It is a 2-pin connector.. This is the direct electrical connection to the coil. Checking for battery voltage at one pin and a pulsing ground signal from the PCM on the other pin during cranking can differentiate a coil failure from a wiring or PCM problem.
• G100 / G101 — Main engine-to-chassis ground straps. Often located on the passenger side of the engine block, sometimes behind a heat shield, connecting to the frame or firewall.. A corroded or broken main engine ground strap is a common issue on JKs and can cause a weak spark across all cylinders, potentially leading to intermittent misfires that are difficult to diagnose. While it may not isolate to just P0302, it can be a contributing factor to poor ignition performance.

Real Owner Repair Stories

• Reddit user in /r/GrandCherokee (with same 3.6L engine) (2017 Jeep Grand Cherokee 3.6L, 110k miles) — Intermittent flashing check engine light with misfire and trouble accelerating, specifically when turning onto an incline. Restarting the vehicle made it run normally.
  ❌ Tried (didn't work) Replaced spark plugs, Replaced ignition coil for cylinder 2
  ✅ What actually fixed it The user was advised by their mechanic that the next step was likely a new fuel injector, as the issue persisted after replacing the common ignition components. The problem was not fully resolved in the thread, but highlights the common misdiagnosis path.

OEM Part Supersession History

• 5184296AD, 5184296AE, 5184296AF, 5184296AG → 5184296AH — The original rocker arms were prone to premature failure of the needle bearings in the roller, leading to ticking noises and misfires. The updated 'AH' part is the latest revision designed for improved durability.
  Heads up: The 'AH' revision is the correct service part for all 2012-2019 Wranglers. Using older stock or non-updated aftermarket parts may lead to a repeat failure.

Model Year Variations Within This Range

• 2012-2013: These model years are most susceptible to the left cylinder head defect covered by warranty extension X56. A P0302 on these years has a very high probability of being the head issue.
• 2014-2018 (JK): These models use a different oil filter housing and oil cooler design than the 2012-2013 models. While not directly related to the misfire cause, it's a key difference when servicing the top of the engine. The cylinder head issue is less common but rocker arm failure remains a significant possibility.
• 2018-2019 (JL): The Wrangler JL, introduced in 2018, uses an upgraded version of the 3.6L Pentastar. While still a 3.6L, it features improvements for efficiency and low-end torque. While many valvetrain components are similar, some parts may not be interchangeable with the JK version.