P0305 on 2020-2025 Jeep Gladiator: Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2020-2025 Jeep GLADIATOR

While any engine can have a misfire from a bad spark plug, the 3.6L Pentastar V6 in the Jeep Gladiator has a well-documented history of valvetrain problems. A P0305 code, especially when accompanied by a ticking or tapping sound, often points to a failed rocker arm and/or lifter. The needle bearings inside the rocker arm can fail, causing the arm to seize or develop excessive play. This action grinds down the corresponding lobe on the camshaft, preventing the valve from opening correctly and leading to a persistent mechanical misfire that a simple tune-up won't fix. Manufacturer TSBs specifically link these misfire codes to "Valvetrain noise," confirming this is a known platform weakness. [Bulletin #09-011-25]

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light is on (solid or flashing)
• Rough or shaky idle
• Engine hesitation or loss of power during acceleration
• Audible ticking or tapping noise from the engine, especially the passenger side valve cover
• Reduced fuel economy
• Vibration from the engine
• Engine fluttering or power loss at high RPM, which can precede the CEL.

Most Likely Causes

1. Failed Rocker Arm and/or Lifter 🔴 High Probability The 3.6L Pentastar V6 has a known design weakness with the needle bearings in the rocker arms, which can fail and cause damage to the camshaft. TSB #09-011-25 explicitly connects misfire codes to 'Valvetrain noise'.
   How to confirm: Listen for a distinct ticking/tapping noise from the top of the engine, specifically the passenger side. A mechanic can confirm by removing the valve cover to inspect the rocker arms and camshaft lobes for wear, scoring, or a loose/seized rocker.
   Typical fix: Replace all rocker arms and lifters on the affected bank (and often both banks as a preventative measure). The camshaft must also be inspected and replaced if its lobes are scored or worn down, which is a common outcome. This is an involved, multi-hour repair.
   Est. part cost: $150-$600
2. Bad Ignition Coil 🟡 Medium Probability
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 3, which is also on the passenger side). Clear the codes and drive. If the code changes to P0303, the ignition coil is faulty.
   Typical fix: Replace the faulty ignition coil. It is often recommended to replace all coils on the same bank or all six at once if they are original and high-mileage.
   Est. part cost: $30-$85
3. Worn or Fouled Spark Plug 🟡 Medium Probability
   How to confirm: After ruling out the coil, remove the spark plug from cylinder 5. Inspect it for wear, cracks, oil fouling, or damage. Compare it to a new plug. An oil-fouled plug can also indicate other issues like a leaking valve cover gasket.
   Typical fix: Replace the spark plug. It is best practice to replace all six spark plugs at the same time for even performance, especially since the intake manifold must be removed to access the driver's side bank.
   Est. part cost: $10-$25
4. Faulty Fuel Injector ⚪ Low Probability
   How to confirm: Listen for the injector's clicking sound with a mechanic's stethoscope. Check the injector's resistance with a multimeter (should be around 11-13 ohms). This is often done after ignition issues are ruled out.
   Typical fix: Replace the fuel injector for cylinder 5. This requires removing the intake manifold.
   Est. part cost: $50-$120

Rare But Worth Checking

• Intake Manifold Gasket Leak: A vacuum leak near cylinder 5 can lean out the air/fuel mixture and cause a misfire. This can be diagnosed with a smoke test. One owner found a damaged lower intake manifold gasket to be the root cause after other repairs failed.
• Low Engine Compression: If all else fails, a compression test is needed. This can indicate more severe internal engine problems like a bad valve, warped cylinder head, or worn piston rings. Critically, a wiped camshaft lobe from a failed rocker arm will also cause low compression.

Diagnosis Steps

1. Scan the vehicle for any other stored trouble codes to get a full picture. Note if codes like P0300 or P0205 are present.
2. Listen carefully to the engine at idle and while revving. A rhythmic ticking or tapping noise from the passenger side valve cover is a strong clue for a valvetrain issue.
3. If no ticking is present, start with the ignition system. Swap the ignition coil from cylinder 5 (passenger side, rear) with the coil from cylinder 3 (passenger side, middle).
4. Clear the codes and drive the vehicle to see if the misfire code returns as P0303. If it does, the ignition coil is bad and needs replacement.
5. If the code remains P0305, swap the spark plugs between cylinders 5 and 3. If the code moves to P0303, the spark plug was the issue.
6. If the misfire still stays on cylinder 5, the problem is likely a fuel injector or a mechanical issue.
7. Test the fuel injector for proper operation (listening for clicks) and electrical resistance (around 11-13 ohms).
8. If a ticking noise was present from the start, or if all ignition and fuel tests for cylinder 5 pass, the next step is mechanical diagnosis. Remove the passenger side valve cover to visually inspect the rocker arms and camshaft lobes for wear, scoring, and damage.
9. If a rocker arm is found to be seized or has play, and/or the camshaft lobe is visibly worn, the valvetrain components must be replaced.
10. If the valvetrain appears normal, perform an engine compression test on cylinder 5 to check for issues like bad valves or rings.

Parts You'll Likely Need

• Ignition Coil (OEM #68223569AD) — A common failure point for misfires. It's responsible for providing the high voltage to the spark plug.
  Trusted brands: Mopar, Delphi, NGK, Denso
  OEM price range: $80-$120
  Aftermarket price range: $30-$70
• Spark Plug (OEM #SP225755AA) — A routine maintenance item that wears out over time, leading to a weak or inconsistent spark.
  Trusted brands: Mopar, NGK, Champion
  OEM price range: $20-$30
  Aftermarket price range: $10-$20
• Rocker Arm & Lifter Kit (OEM #5184296AH (Rocker Arm)) — Due to a known issue with the 3.6L Pentastar, the rocker arm bearings can fail, causing a misfire and ticking noise. This is a primary suspect if ignition parts don't solve the code. Part 5184296AH is an updated design that supersedes previous versions (-AD, -AE, -AF, -AG).
  Trusted brands: Mopar, Melling, Mahle
  OEM price range: $250-$400
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• P0300 — If the valvetrain issue is severe or multiple components are failing, the misfire may become random or affect multiple cylinders, triggering a P0300 (Random/Multiple Cylinder Misfire) code.
• P0205 — This code indicates a fault in the cylinder 5 injector circuit. It can appear alongside P0305 if the injector or its wiring is the root cause of the misfire. If P0205 is present, diagnose the injector first.

Technical Service Bulletins (TSBs) & Recalls

• 09-011-25: Links P0301-P0306 misfire codes with customer complaints of rough idle and valvetrain noise.
• 18-061-24: Lists P0305-00 as a potential trouble code related to a software update.
• 18-002-22 REV. A: Lists P0305-00 as a potential trouble code related to a software update.
• 09-013-20 REV. A: Links P0301-P0306 misfire codes with customer complaints of a rough running engine.

Platform-Specific Known Issues

• Valvetrain Wear: The 3.6L Pentastar V6 is known for premature failure of rocker arm bearings, which can seize and wear down the camshaft lobes. This results in a ticking noise and a persistent misfire code like P0305. TSB #09-011-25 directly links misfire DTCs with 'Valvetrain noise' and TSB #09-013-20 REV. A links them to a 'Rough running engine'. This is the single most discussed major failure for this code on Gladiator and Wrangler forums.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance — expected: 12.0 - 12.5 Ohms. Failure: A significantly higher reading (e.g., over 25 Ohms) or an open circuit indicates a failed injector. One real-world case showed a bad injector reading over 60 Ohms.
• Ignition Coil Primary Resistance (OEM) — expected: 0.4 to 2 Ohms. Failure: A reading outside this range suggests a faulty primary winding.
• Ignition Coil Secondary Resistance (OEM) — expected: 6,000 to 10,000 Ohms. Failure: A reading outside this range suggests a faulty secondary winding.
• Mode 6 Misfire Counter — expected: Low, infrequent counts on all cylinders during normal operation.. Failure: A rapidly increasing count on a single cylinder (e.g., cylinder 5) confirms an active misfire that the PCM is tracking, even before a permanent code is set.

Scan Tool Commands That Help

• wiTECH 2.0 (OEM) or advanced aftermarket scanner: Cylinder Power Balance Test — This test should be used after basic spark and coil swaps fail to identify the issue. The tool deactivates one cylinder at a time and measures the drop in RPM. A cylinder with a smaller RPM drop than the others is not contributing as much power, confirming the location of the misfire without moving parts around.
• wiTECH 2.0 (OEM) or advanced aftermarket scanner: View Misfire Counters (Mode 6 Data) — Use this to confirm which cylinder is misfiring in real-time, especially for intermittent issues. Watching the live counts for each cylinder can reveal which one is accumulating misfire events during a test drive, confirming the P0305 is accurate and not a random event.

Wiring & Ground Locations

• G927A — On the engine block, under the lower intake manifold.. TSB 08-111-21 identifies a faulty engine ground eyelet at this location for some 2021 Gladiators. A poor ground here can cause rough running and set various DTCs. While the TSB doesn't list P0305 specifically, a bad engine ground can cause erratic behavior, including misfires.
• Main Engine to Chassis Ground — Typically a thick cable running from the engine block to the firewall or frame rail near the battery.. A corroded or loose main engine ground can cause a host of electrical issues, including weak spark, which can lead to misfires. It's a basic check that is often overlooked.

Real Owner Repair Stories

• Reddit user on r/Jeep (2014 Jeep Wrangler (JK 3.6L)) — Persistent P0305 code for over a year.
  ❌ Tried (didn't work) Replaced spark plugs (worked temporarily), Replaced coil packs and spark plugs again (worked temporarily)
  ✅ What actually fixed it A teardown revealed a 'wiped cam' lobe. The final fix, covered by warranty, was to replace the camshaft, all rocker arms, and check the valve springs and clearances.
• YouTube channel 'yellerlife' (2015 Jeep Wrangler JKU (3.6L V6)) — P0303 code (different cylinder, same engine/diagnosis) with audible misfire.
  ❌ Tried (didn't work) Swapped ignition coils; misfire did not move., Swapped spark plugs; misfire did not move.
  ✅ What actually fixed it An ohms test on the fuel injectors revealed the misfiring cylinder's injector had a resistance of ~65 ohms, while good injectors measured ~12 ohms. Replacing the faulty fuel injector resolved the misfire.

OEM Part Supersession History

• 5184296AD, 5184296AE, 5184296AF, 5184296AG → 5184296AH — The rocker arm for the 3.6L Pentastar has been updated multiple times to address the premature failure of the needle bearings. The 'AH' version is the latest revision intended to be more durable.
  Heads up: All previous versions should be replaced with the latest 'AH' part. Using older stock or a mix of old and new rocker arms is not recommended, especially when repairing a known failure.

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 harness eyelet. This can cause rough running and multiple engine-related DTCs.