P0305 on 2017-2026 Chrysler Pacifica: Cylinder 5 Misfire Causes and Fixes

What's Unique About the 2017-2026 Chrysler Pacifica

The 3.6L Pentastar V6 in the Pacifica is a very common engine, but it has a well-documented history of valvetrain issues, specifically with rocker arm bearings failing. While a P0305 code is often just a simple ignition problem, on this platform it can be an early symptom of this deeper mechanical issue. This is often accompanied by a distinct ticking noise, sometimes called the 'Pentastar tick'. A seized rocker arm can grind down the camshaft lobe, leading to a persistent misfire that a simple tune-up will not fix. Additionally, some owner reports link a P0305 code with coolant loss, suggesting a potential head gasket leak into cylinder 5.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or shaky idle
• Hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Engine vibration
• A distinct ticking or tapping sound from the top of the engine, which may increase with RPM
• Reduced fuel economy
• Unexplained loss of coolant from the reservoir

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability → Shop Ignition Coil Coil-on-plug systems are exposed to constant high heat and vibration, making them a common failure point on most modern engines.
   How to confirm: Swap the ignition coil from cylinder 5 with another cylinder (e.g., cylinder 3, also on the rear bank). Clear the codes and drive. If the code changes to P0303, the ignition coil is faulty.
   Typical fix: Replace the failed ignition coil. It is highly recommended to replace the spark plug at the same time.
   Est. part cost: $30-$75
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a regular maintenance item with a finite lifespan. An old or oil/coolant-fouled plug can no longer create a strong enough spark to ignite the air-fuel mixture.
   How to confirm: After confirming the coil is good, inspect the spark plug for wear, carbon buildup, or fouling from oil or coolant. You can also swap the plug to another cylinder to see if the misfire follows it.
   Typical fix: Replace the spark plug in cylinder 5. It is best practice to replace all six spark plugs 🎬 Watch: Step-by-step guide to replacing spark plugs and coils. if they are near the end of their service interval (typically 100,000 miles).
   Est. part cost: $10-$25 per plug
3. Failed Rocker Arm / Cam Follower 🟡 Medium Probability → Shop Engine Rocker Arm The 3.6L Pentastar engine is known for issues with the needle bearings in the rocker arms failing. This causes the arm's roller to seize and grind on the camshaft lobe, leading to insufficient valve lift and a persistent misfire.
   How to confirm: Listen for a distinct ticking or tapping noise from the upper engine. Definitive diagnosis requires removing the rear valve cover for visual inspection of the rocker arms and camshaft lobes for scoring, wear, or damage.
   Typical fix: Replace all rocker arms and hydraulic lifters on the affected cylinder head (Bank 1 for cylinder 5). If the camshaft lobes are scored or worn down, the camshaft(s) must also be replaced. This is a labor-intensive repair. 🎬 Watch: Important warnings and tips for fixing the Pentastar tick.
   Est. part cost: $200-$1,800. Rocker arms and lifters may cost $200-$400, but if camshafts are also required, the parts cost can increase significantly.
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector
   How to confirm: Check for a pulse signal at the injector wiring harness with a 'noid' light. A more definitive test is to swap the injector with another cylinder, but this is labor-intensive as it requires removing the fuel rail. Resistance can also be checked with a multimeter; normal is around 12 ohms.
   Typical fix: Replace the faulty fuel injector. This is often done while the intake manifold is already off for other diagnostics.
   Est. part cost: $50-$120

Rare But Worth Checking

• Leaking Head Gasket: Several owner reports for the Pacifica and other 3.6L Pentastar vehicles connect a P0305 code with unexplained coolant loss. A small leak can cause the spark plug to become fouled by coolant, leading to a misfire. A pressure test of the cooling system or using a borescope to look for coolant inside the cylinder 🎬 See how to inspect cylinder 5 before starting major repairs. can help confirm this.
• Leaking Intake Manifold Gasket: → Shop Engine Intake Manifold A vacuum leak near the cylinder 5 intake runner can lean out the air-fuel mixture enough to cause a misfire. This is more likely after the intake has been removed for other service.
• Low Cylinder Compression: Internal engine damage such as a bad valve, worn piston rings, or a blown head gasket can cause a loss of compression, leading to a misfire. This is a serious mechanical issue requiring a compression and/or leak-down test to diagnose.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0305 is present. Note if the Check Engine Light is steady or flashing.
2. Listen for any unusual noises, especially a rhythmic ticking sound from the top rear of the engine, which points towards a possible rocker arm issue.
3. Check the coolant reservoir level. If it is low without any visible external leaks, suspect a possible head gasket leak.
4. Perform an 'ignition coil swap'. Move the ignition coil from cylinder 5 to another cylinder on the same bank (like cylinder 3). Clear the codes, run the engine, and see if the misfire code moves to the new cylinder (P0303). If it does, the coil is bad.
5. If the misfire remains on cylinder 5, inspect the spark plug. Accessing it requires removing the upper intake manifold. Check the plug for wear, damage, or fouling from oil or coolant. Replace as needed.
6. While the intake is off, it is a good time to test the fuel injector. A 'noid' light can confirm if the injector is receiving a signal. You can also check its resistance with a multimeter.
7. If ignition and fuel components check out, the issue is likely mechanical. A cooling system pressure test and a check for combustion gases in the coolant can identify a head gasket leak.
8. If a ticking noise is present or other tests are inconclusive, remove the rear valve cover to visually inspect the valvetrain. Look for a failed/loose rocker arm and check for scoring or damage on the camshaft lobes.
9. As a final step, a cylinder compression test and a leak-down test should be performed to check the overall mechanical health of cylinder 5.

Parts You'll Likely Need

• Ignition Coil (OEM #68320417AA (supersedes 5149199AA)) — This is the most common failure point for a single-cylinder misfire and the first component to test.
  Trusted brands: Mopar, NGK, Delphi
  OEM price range: $50-$80
  Aftermarket price range: $30-$60
• Spark Plug (OEM #SP142510AC) — As a routine maintenance item, a worn spark plug is a frequent cause of misfires.
  Trusted brands: Mopar, NGK, Champion
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Upper Intake Manifold Gasket Set (OEM #5184562AC) — Required for reassembly after accessing the rear cylinder bank for any service on cylinder 5 (coil, plug, or injector).
  Trusted brands: Mopar, Fel-Pro, Mahle
  OEM price range: $30-$50
  Aftermarket price range: $20-$40
• Engine Rocker Arm (OEM #5184296AH) — If a ticking noise is present, a failed rocker arm is a probable cause. This part number has been revised multiple times, suggesting an attempt to improve the design.
  Trusted brands: Mopar, Melling, SKP
  OEM price range: $18-$30 per arm
  Aftermarket price range: $8-$15 per arm

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent, severe enough to affect crankshaft timing broadly, or if other cylinders are also misfiring (e.g., due to a widespread rocker arm issue), a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0305.
• P0205 — This code for 'Injector Circuit/Open - Cylinder 5' can appear with P0305, strongly indicating the problem is with the fuel injector for cylinder 5 or its wiring, rather than spark or a mechanical issue.

Technical Service Bulletins (TSBs) & Recalls

• TSB #09-011-25 (for a different Chrysler model but same engine family) explicitly links misfire DTCs with 'Valvetrain noise', corroborating the connection between the code and potential rocker arm failure.
• Older TSBs like #09-002-14 and the related X56 warranty extension were for a different issue concerning the left cylinder head on 2011-2013 models (cylinders 2, 4, 6) and are generally not applicable to the P0305 rocker arm failure on a 2017+ Pacifica.

Platform-Specific Known Issues

• The 3.6L Pentastar V6 has a known design issue with rocker arm bearings that can fail prematurely, causing a misfire and a distinct 'Pentastar tick'. This can eventually lead to camshaft damage if not addressed.
• Some owners have reported P0305 in conjunction with coolant loss, pointing to a potential for head gasket failure on cylinder 5, which is on the hotter rear bank of the engine.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance — expected: 12.0 - 12.5 Ohms. Failure: A significantly higher reading (e.g., over 20 Ohms), an open circuit (infinite resistance), or a short (near 0 Ohms) indicates a faulty injector.
• Ignition Coil Primary Resistance — expected: 0.4 - 2.0 Ohms. Failure: A reading outside this range suggests a faulty coil. However, this test is not always conclusive; swapping the coil to another cylinder is the most reliable test.
• Ignition Coil Secondary Resistance — expected: 6,000 - 10,000 Ohms. Failure: A reading outside this range suggests a faulty coil. Heat-related failures may not show up in a cold resistance test.
• Cylinder Compression (Wet with Coolant) — expected: Approx. 135 PSI (for a healthy cylinder). Failure: An abnormally high reading, such as 250-270 PSI, can indicate coolant has leaked into the cylinder, which is incompressible and spikes the pressure reading.
• Fuel Pressure — expected: ~43.5 PSI (3 Bar). Failure: Low fuel pressure would typically affect multiple cylinders or cause a lean condition code, but it's a foundational value to check. The Pentastar uses a returnless system.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Counters: A professional scan tool can access Mode $06 data, which shows the raw misfire count for each individual cylinder over the current and previous drive cycles. This allows a technician to see intermittent misfires on cylinder 5 that haven't yet reached the threshold to trigger the P0305 code. (see via Use a scan tool with Mode $06 (On-Board Diagnostic Monitors) capability. Look for Test IDs related to misfire counts (e.g., TID $A1-$AC).)

Scan Tool Commands That Help

• wiTECH, Autel, XTOOL, or other capable bidirectional scanner: SGW (Security Gateway) Bypass — On all 2018 and newer Pacificas, this is not a command but a mandatory physical step. A 12+8 adapter cable must be connected to the module behind the dash to enable any bidirectional controls or advanced diagnostics.
• wiTECH or equivalent bidirectional scanner: Injector Test / Buzz Test — After confirming spark is good, this command allows you to individually activate the cylinder 5 fuel injector. You should hear an audible click. If not, it points to a failed injector or a wiring/PCM driver issue. This is useful when P0205 is also present.
• wiTECH or equivalent bidirectional scanner: Cylinder Contribution Test — This function analyzes crankshaft speed variations as it disables cylinders one by one. It can help confirm that cylinder 5 is the one not contributing power, verifying the P0305 code before tearing into the engine.

Wiring & Ground Locations

• G100 / G101 / G102 — Primary engine and chassis grounds located in the engine compartment, often on the frame rail behind a headlight assembly or directly on the engine block.. A loose or corroded main ground can cause weak spark or erratic injector behavior, leading to misfires that can be difficult to trace. Verifying main grounds are clean and tight is a crucial early step.
• Engine Ground Strap (P/N 68316197AA) — Connects the engine block to the chassis to ensure a solid ground path.. Corrosion or breakage of this strap can lead to a host of electrical issues, including misfires. The PCM and ignition system rely on this ground for a stable reference.
• Cylinder 5 Coil/Injector PCM Pins — At the main Powertrain Control Module (PCM) connectors. A vehicle-specific wiring diagram is required to identify the exact pin numbers for the cylinder 5 ignition coil control and fuel injector control circuits.. To definitively rule out a wiring harness issue, a continuity test from the component's connector back to the corresponding PCM pin is necessary. This finds any breaks or shorts in the harness.

Real Owner Repair Stories

• NHTSA ODI #11445531 (2018 Chrysler Pacifica) — Check engine light on with code P0305.
  ❌ Tried (didn't work) Not specified
  ✅ What actually fixed it The cause was a head gasket leaking coolant into cylinder 5. The head gasket was replaced.
• NHTSA ODI #11531350 (2019 Chrysler Pacifica) — Intermittent check engine light.
  ❌ Tried (didn't work) Not specified, but implies ignition/mechanical was considered first.
  ✅ What actually fixed it The vehicle had both P0305 and P0205 (Injector Circuit/Open) codes. The root cause was the fuel injector for cylinder 5 or its wiring, not an ignition or mechanical issue.
• Reddit user, r/MechanicAdvice (2015 Jeep Wrangler 3.6L Pentastar (same engine family)) — P0303 misfire (different cylinder, same diagnostic principle).
  ❌ Tried (didn't work) Swapped ignition coil to another cylinder, misfire did not move., Swapped spark plug to another cylinder, misfire did not move.
  ✅ What actually fixed it Performed a resistance test on the fuel injectors. The good cylinder read 12.2 Ohms, while the misfiring cylinder's injector read 63.2 Ohms. Replacing the faulty fuel injector resolved the misfire.
• YouTube user 'mrdavetrouble' (2017 Chrysler Pacifica) — Persistent P0305, small amount of coolant consumption, visible white smoke from exhaust.
  ❌ Tried (didn't work) Initial diagnostics pointed to a blown head gasket.
  ✅ What actually fixed it Owner used Blue Devil head gasket sealer as an alternative to a mechanical repair. A follow-up comment noted the repair was still holding after 5,000 miles.

"I Checked Everything" — The Actual Cause

• A common scenario that mimics a 'smoke test clean' situation is a micro-leak in the head gasket. The leak is too small to be detected by a standard combustion gas test and doesn't cause obvious symptoms like heavy smoke or oil contamination. However, when the engine is shut off, the pressurized cooling system slowly weeps a small amount of coolant onto the piston. On the next startup, this coolant fouls the spark plug, causing a misfire code until the coolant is burned off. The engine may then run perfectly fine, making diagnosis difficult.

When the Usual Fixes Don't Work

• While ignition coils and spark plugs are the most common cause, do not repeatedly replace them if the P0305 code returns. On this specific engine, a recurring P0305, especially when accompanied by a ticking noise or slow coolant loss, is highly likely to be a deeper mechanical issue. A real-world case from the NHTSA database showed a P0305 accompanied by a P0205 (Injector Circuit) code, where the final fix was the fuel injector itself, not the more common coil or plug. Another case showed a confirmed head gasket leak was the root cause.

OEM Part Supersession History

• 5184296AD, 5184296AE, 5184296AF, 5184296AG → 5184296AH — This is the Engine Rocker Arm. The extensive revision history suggests ongoing attempts by the manufacturer to remedy the well-known issue of premature needle bearing failure in the roller.
• 5149199AA → 68320417AA — This is the Ignition Coil. Standard part design improvement and supplier changes over the vehicle's lifecycle.

Model Year Variations Within This Range

• 2018-2026: Introduction of the Security Gateway Module (SGW). On these model years, performing any bidirectional control (like an injector buzz test) or clearing codes in certain modules requires a scan tool with proper FCA licensing (e.g., AutoAuth) and a physical 12+8 bypass adapter cable connected behind the dashboard. A simple OBD-II reader can only read powertrain codes.

Diagnostic Flowchart

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0303 — Cylinder 3 Misfire Detected. This code will appear if you perform the recommended diagnostic step of swapping a faulty ignition coil from cylinder 5 to cylinder 3.
• P0302 — Cylinder 2 Misfire Detected. Mentioned in older TSB #09-002-14 regarding left cylinder head issues on the 3.6L Pentastar engine.
• P0304 — Cylinder 4 Misfire Detected. Also associated with the left cylinder head failure outlined in TSB #09-002-14.
• P0306 — Cylinder 6 Misfire Detected. The third cylinder affected by the left cylinder head issues described in TSB #09-002-14.
• P0205 — Injector Circuit/Open - Cylinder 5. Often checked alongside P0305 when diagnosing a potential fuel injector failure on cylinder 5.

Frequently Asked Questions