P0302 on 2020-2025 Jeep Gladiator 3.6L: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2020-2025 Jeep GLADIATOR

On the Jeep Gladiator's 3.6L Pentastar V6 engine, cylinder 2 is located on the driver's side, at the very front of the engine. Unlike the cylinders on the passenger side (1, 3, 5), accessing cylinder 2 (and 4, 6) requires removing the upper intake manifold, which adds significant labor time (1-2 hours) 🎬 Watch: Step-by-step guide to removing the intake manifold and spark plugs. and complexity to the repair. While the most common causes are simple ignition parts, the 3.6L Pentastar family of engines has a documented history of valvetrain issues, such as rocker arm and lifter failures, which can also lead to persistent misfire codes, sometimes preceded by a distinct ticking noise.

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
• Flashing or solid Check Engine Light
• Noticeable loss of power and acceleration
• Engine hesitation or stumbling
• Smell of raw fuel from the exhaust
• Increased fuel consumption

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point due to constant heat cycles. In one documented case on a 2020 Gladiator, an aftermarket performance coil pack failed, causing a P0302 code.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder on the same bank (e.g., cylinder 4). Clear the codes with a scanner and drive the vehicle. If the code changes to P0304 (Cylinder 4 Misfire), the coil is confirmed bad.
   Typical fix: Replace the faulty ignition coil. Since accessing this cylinder bank requires removing the intake manifold, many owners and shops choose to replace all three driver's side coils (2, 4, 6) and all six spark plugs at the same time to save on future labor.
   Est. part cost: $40-$80
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a regular maintenance item. A known manufacturing issue with original spark plugs on some 2020-2021 models can cause an internal crack, leading to misfires. TSB 09-013-20 REV. A addresses this by recommending the replacement of all six spark plugs if a misfire code is present.
   How to confirm: After confirming the coil is good, remove the spark plug from cylinder 2. Inspect it for wear (eroded electrode), damage (cracked porcelain), or heavy deposits of oil or carbon. Compare it to a new plug.
   Typical fix: Replace the spark plug. It is best practice to replace all six spark plugs at the same time to ensure even performance, especially given the labor to access the driver's side.
   Est. part cost: $10-$25 per plug
3. Clogged or Faulty Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Fuel injectors can become clogged with deposits over time or fail electrically. Some owners on forums report resolving misfires that occur only under hard acceleration by replacing the fuel injector after ignition components were ruled out.
   How to confirm: If ignition parts are good, the injector is the next suspect. A professional can test the injector's flow rate and electrical resistance. A DIY method is to swap the injector with another cylinder, but this is labor-intensive as it also requires removing the intake manifold and fuel rail.
   Typical fix: Replace the fuel injector for cylinder 2. Some owners first attempt to use a quality fuel system cleaner as a less invasive first step.
   Est. part cost: $70-$150
4. Engine Mechanical Fault (Rocker Arms/Lifters) ⚪ Low Probability The 3.6L Pentastar engine is known to develop valvetrain issues, particularly with rocker arm needle bearings failing, which can seize and damage the camshaft lobe. This prevents the valve from opening correctly and causes a misfire, often accompanied by a ticking or tapping sound 🎬 See how to identify and replace failing rocker arms. from the upper engine.
   How to confirm: This is a more complex diagnosis. It often starts with a ticking noise from the top of the engine. A compression test and cylinder leak-down test can point to a mechanical issue. Visual inspection requires removing the valve cover and camshafts.
   Typical fix: Requires replacing the affected rocker arms and potentially the lifters and camshaft. This is a significant repair best left to a professional or experienced DIYer.
   Est. part cost: $200-$600 for parts, plus significant labor

Rare But Worth Checking

• Leaking Head Gasket: A forum user on JeepGladiatorForum.com traced a persistent, intermittent misfire to a head gasket leak allowing coolant into the cylinder. This was confirmed via an oil analysis showing glycol, and the dealer replaced the head gasket under warranty. This is not common but is a possibility if other diagnostics fail and coolant loss is observed.
• Wiring Harness Issue: A poor pin connection in one of the main engine wiring harness connectors can cause an intermittent misfire. One owner of a 3.6L Jeep found a recessed pin in a large connector that, when wiggled, would cause or clear the misfire.
• PCM Software/Cam Phaser Sync: In some cases, a misfire can be caused by a software glitch or a loss of synchronization between the camshaft and crankshaft. A YouTube video demonstrated a fix for a persistent misfire on a 2020 Gladiator by using an advanced scan tool to perform a "phaser exhaust cleaning" and "reset memory" function, which resolved a hard fault that occurred when the engine entered closed loop. A cam/crank relearn procedure may also be necessary.

Diagnosis Steps

1. Connect an OBD-II scanner to confirm the P0302 code and check for any other stored codes. Note freeze frame data if available.
2. Locate cylinder 2: It is the front-most cylinder on the driver's side of the engine.
3. Since access requires intake manifold removal, a full tune-up is recommended. However, to diagnose, you must first remove the upper intake manifold to access the driver's side components.
4. Once the manifold is off, swap the ignition coil from cylinder 2 with the coil from cylinder 4 (the middle cylinder on the same bank).
5. Temporarily reinstall the intake manifold (or use a smoke machine to check for other leaks while it's off), clear the codes, start the engine, and let it run. Re-scan for codes.
6. If the code is now P0304, you have a bad ignition coil. Replace it.
7. If the code remains P0302, the coil is likely good. Proceed to inspect and replace the spark plug for cylinder 2. Check for cracks or manufacturing defects as noted in TSB 09-013-20 REV. A. It is highly recommended to replace all 6 plugs.
8. If the code still remains P0302, inspect the wiring and connector for the cylinder 2 ignition coil and fuel injector. Look for damage, corrosion, or loose pins.
9. If wiring is intact, the fuel injector is the next likely cause. At this point, you can swap the injector with another cylinder to confirm, or replace it.
10. If all of the above steps do not resolve the issue, listen for a ticking noise from the upper engine. Perform a compression test on cylinder 2 to check for mechanical engine problems like worn rocker arms, lifters, or a leaking head gasket.
🎬 Watch: Complete walkthrough for replacing rocker arms, lifters, and camshafts.

Parts You'll Likely Need

• Ignition Coil (OEM #68444549AA) — This is the most frequent cause of a single-cylinder misfire on modern engines.
  Trusted brands: Mopar, NGK, Denso
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plug (OEM #SP149125AE) — A common wear item that can become fouled or worn out. TSB 09-013-20 REV. A notes a manufacturing defect in original plugs on some 2020-2021 models. This part number supersedes SP149125AD.
  Trusted brands: Mopar (Champion), NGK, Autolite
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Upper and Lower Intake Manifold Gaskets (OEM #05184562AC (Lower)) — These must be replaced when removing the intake manifold to access the driver's side cylinders (2, 4, 6) for service. Reusing old gaskets is not recommended and can cause vacuum leaks.

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or affects other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0302.
• P0304, P0306 — If the root cause is something that affects the entire driver's side cylinder bank (like a vacuum leak near that side of the intake manifold or a valvetrain issue on that bank), you may also get misfire codes for cylinders 4 and 6.

Technical Service Bulletins (TSBs) & Recalls

• Addresses a known manufacturing defect causing internal cracks in spark plugs on certain 2021 model year vehicles, leading to misfire codes (P0301-P0306). The fix is to replace all six spark plugs.
• This TSB is for a PCM software update to address a list of various DTCs, including P0302. It suggests that in some cases, a software flash may resolve certain conditions causing the code.

Platform-Specific Known Issues

• A thread on JeepGladiatorForum.com titled 'Survey- For those with misfire issues' contains multiple owner accounts of P0302. One user with a 2021 Gladiator Rubicon at 5,500 miles experienced the code and noted the misfire was much worse when in gear with the brake applied.
• Another user in the same thread reported their P0302 issue was ultimately resolved by the dealer performing a 'cam/crank relearn' procedure.
• A YouTube video from the channel 'Lite Brite' documented a P0302 code on a 2020 Gladiator after installing aftermarket RIPP coil packs. The issue was resolved by replacing the failed aftermarket coil on cylinder 2 with another new one. The video provides a good visual of the intake manifold removal process.
• TSB 09-013-20 REV. A was issued for 2021 Gladiators (and other 3.6L models) built between Sept 2, 2020 and Nov 12, 2020 due to a known manufacturing issue causing internal cracks in the spark plugs, leading to misfire codes including P0302. The prescribed fix is to replace all six spark plugs.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance — expected: OEM spec is not published, but a high-performance aftermarket equivalent (RIPP) measures 0.59Ω. A reading significantly different from the other coils on the engine would indicate a problem.. Failure: An open circuit (infinite resistance) or a reading that is an outlier compared to other coils.
• Live Misfire Counts (Mode $06 or OEM Scanner) — expected: Ideally zero on a healthy, warm engine. A few counts on a cold start can be normal, but they should not increment continuously.. Failure: A continuously rising count on cylinder 2 while other cylinders show few or no counts. This confirms the misfire is isolated to cylinder 2.

Hidden / Shadow Codes Worth Checking

• Live Misfire Data: Beyond the stored P0302 code, dealer-level scanners like wiTECH can display live misfire counters for each individual cylinder. This allows a technician to see the misfires as they happen, even if they aren't frequent enough to set a code immediately. This is similar to Mode $06 data on generic OBD-II scanners. (see via Connect a wiTECH scan tool, navigate to the PCM/ECM, and select the OBD II monitors to view 'Which cylinder is misfiring'. Some advanced consumer scanners like J-Scan also offer this functionality.)

Scan Tool Commands That Help

• wiTECH or equivalent (Appcar DiagFCA, HP Tuners): Cam/Crank Relearn (also called TLC Relearn) — This procedure should be performed after replacing a camshaft, crankshaft, their respective sensors, or timing components. It is also used to resolve persistent, intermittent misfires that don't have an obvious component cause, as the PCM may have lost the precise relationship between the cam and crank sensors. The engine must typically be warmed up to operating temperature (e.g., above 158°F / 70°C) before the routine can be run successfully.
• wiTECH: Clear Mis-fire TLC — This function is used to clear the 'Transmission Self Learning' values related to misfire detection. It is often performed as part of a larger diagnostic or relearn procedure when troubleshooting persistent misfire codes.

Wiring & Ground Locations

• G927A — On the engine block, under the lower intake manifold on the right (passenger) side.. TSB 08-111-21 was issued for some 2021 Gladiators/Wranglers due to a faulty ground eyelet at this location. While the TSB lists codes for VVT solenoids and cam actuators, a poor engine ground can cause a wide range of intermittent electrical issues, including misfires. It's a critical point to inspect if electrical causes are suspected.
• Main Chassis Grounds — Key locations include a ground point on the inner fender behind the airbox (driver side), a point near the battery on the passenger fender, and points on the frame behind the front passenger wheel.. Poor engine-to-chassis grounds can cause unstable voltage for the ignition coils and PCM, leading to weak spark and misfires. Verifying these main grounds are clean and tight is a fundamental step in diagnosing any electrical issue.
• Cylinder 2 Injector/Coil Harness — Runs across the driver's side of the engine, with the connector for cylinder 2 at the front. The harness is routed near hot and vibrating components.. Chafing or heat damage to the wiring for the cylinder 2 ignition coil or fuel injector can cause an open or short, directly leading to a P0302 code. A visual and physical inspection of the harness loom in this area is crucial.

Real Owner Repair Stories

• JeepGladiatorForum.com user (Jeep Gladiator 3.6L) — Intermittent Check Engine Light with P0302, especially after a hot restart and under light load.
  ❌ Tried (didn't work) Initial dealer diagnosis could not replicate the issue in the service bay.
  ✅ What actually fixed it The dealer found a STAR bulletin matching the symptoms and performed a Cam/Crank relearn procedure, which resolved the misfire.
• JeepGladiatorForum.com user 'Jeepmonster' (Jeep Gladiator (year not specified)) — Intermittent P0302 and P0303 codes that occurred over a period of years, along with gradual coolant loss.
  ❌ Tried (didn't work) Using fuel additives., Switching to higher octane fuel., First dealership was unable to find any issue.
  ✅ What actually fixed it A second dealership diagnosed a leaking head gasket. An oil analysis confirmed the presence of glycol (coolant) in the engine oil. The head gasket was replaced under warranty.
• YouTube channel 'Lite Brite' (2020 Jeep Gladiator, 28,000 miles) — Stumbling, running rough, and a flashing check engine light with code P0302 while driving on the highway. Smell of unburnt fuel.
  ❌ Tried (didn't work) The owner suspected multiple potential causes including spark plugs, ECM, or valvetrain issues.
  ✅ What actually fixed it The owner had recently installed aftermarket RIPP high-performance ignition coils. He swapped the cylinder 2 coil with a stock OEM coil, and the misfire was resolved. The aftermarket coil had failed.

"I Checked Everything" — The Actual Cause

• In cases of a slow head gasket leak, a smoke test for vacuum leaks will come back clean because the leak is internal (from a coolant passage into the cylinder), not external (unmetered air entering the intake). The actual cause is coolant contaminating the combustion process, which fouls the spark plug and prevents a proper spark. This is often diagnosed via a chemical block test, a cylinder leak-down test showing bubbles in the radiator, or an oil analysis showing coolant contamination.

When the Usual Fixes Don't Work

• While ignition components are the most common cause, several owner reports confirm that a P0302 code persisted after replacing coils and plugs. In one case, the final fix was a 'Cam/Crank Relearn' procedure performed by the dealer, indicating a software or sensor synchronization issue rather than a hard part failure. In another documented case, the root cause was a slow head gasket leak, which was only found after the owner noticed gradual coolant loss and requested a more in-depth diagnosis that included an oil analysis.

Model Year Variations Within This Range

• 2021: A specific batch of 2021 Gladiators built between October 13, 2020, and October 17, 2020, are subject to TSB 08-111-21 for a faulty engine ground eyelet (G927A) that can cause various electrical and engine running issues.
• 2024-2025: The 2024 model year introduced a significant facelift with a new grille and a standard 12.3-inch infotainment screen. However, the 3.6L Pentastar V6 engine and its specifications (285 hp, 260 lb-ft torque) remain unchanged from previous years. The EcoDiesel engine option was discontinued for 2024.