P0305 on Jeep: How to Diagnose & Fix
Cylinder 5 Misfire Detected
3 Jeep models · 5 documented issues · 3 critical · $180-$7,500 repair
P0305 on Jeep by model: symptoms, diagnosis and fix
HEMI-equipped Grand Cherokees can develop the characteristic MDS lifter tick. This ticking noise is most noticeable at idle and during light throttle. While often not immediately harmful, it indicates lifter wear from the MDS cylinder deactivation system.
Common Symptoms
- Ticking noise at idle
- Tick follows engine RPM
- Noise from top of engine
- Tick more pronounced when warm
- Noise comes and goes
How to Fix
Use quality synthetic oil meeting Chrysler MS-6395 spec. Consider MDS delete kit for permanent solution. Some owners have replaced lifters and camshaft under extended warranty. Regular oil changes help minimize tick progression.
Owner tips & cautions
- TipRegular oil changes help minimize tick progression.
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
Sources for this issue (1)
The updated/'Upgrade' 3.6L Pentastar V6 (used on later WK2 and the WL fifth-gen) suffers premature wear of the intake rocker-arm roller bearings and/or intake camshaft lobes, traced by TSB to a manufacturing issue. As the rocker bearing or cam lobe wears, the valve no longer opens fully, producing a distinct ticking noise and a misfire on the affected cylinder; if ignored the failing rocker can damage the camshaft. This is a separate failure from the early-2011-2013 left-head defect and from the 5.7 HEMI MDS lifter — it affects the V6 valvetrain across both generations.
Common Symptoms
- Cylinder-specific misfire code
- Ticking/tapping noise from the valvetrain
- Rough idle, hesitation, check-engine light
- Misfire that does not move when coil/plug is swapped
- Reduced power
How to Fix
Diagnose a cylinder-specific misfire accompanied by a valvetrain tick with a scope/inspection of the intake rocker arms and camshaft lobes. Replace worn rocker arms and, where the cam lobe is scored, the camshaft, per the applicable Pentastar Upgrade TSB; address promptly to avoid camshaft and follow-on damage. Replace spark plug/coil first only to rule out the easy cause — a persistent misfire with a tick is valvetrain, not ignition.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mopar right intake-camshaft service kitOEMMopar 68661147AB
Complete FCA bulletin repair after right-bank intake high-lift lobe/rocker wear is confirmed Fitment/availability: 68661147AB supersedes 68661147AA and is the right-side kit named in TSB 09-011-25. Confirm VIN, ERC/ERG sales code, build/…
- Genuine Mopar left intake-camshaft service kitOEMMopar 68661146AA
Complete FCA bulletin repair after left-bank intake high-lift lobe/rocker wear is confirmed Fitment/availability: 68661146AA is the left-side kit named in TSB 09-011-25. Confirm VIN, ERC/ERG sales code, build/mileage scope and left-bank …
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Owner tips & cautions
- WarningDo not order a camshaft kit from a misfire code alone. FCA says the symptom may be related to cam/rocker wear, so the high-lift lobe and slider on the indicated bank must be inspected first.
- TipConfirm right versus left bank before ordering. FCA provides two different complete kits, and each already includes the camshaft, rocker arms, sealer, and gaskets for that side.
- WarningThe WL bulletin scope ends at the August 19, 2024 build cutoff even though model-year coverage extends through 2025. Verify the VIN/build record and ERC or ERG sales code.
Sources for this issue (1)
The 4.7L SOHC PowerTech V8 (2006-2009 Commander) presses hard steel valve seats into aluminum cylinder heads. Any overheat event - and the XK's cooling system is itself a weak point - lets the aluminum head grow away from the seat, loosening it. The seat then drops into the combustion chamber, or the head cracks between the valve seats. The failure is usually sudden: a healthy-running engine develops a violent single-cylinder misfire, a hammering noise and total loss of compression in that hole within minutes. Commander owners report it most often on the 4.7 after a cooling-system incident, and Chrysler's 2005-2007 4.7 heads are the ones most cited. Compression on the dead cylinder reads near zero; a borescope shows the seat lying on the piston crown or a valve pocket that has been pounded out.
Common Symptoms
- Sudden severe misfire on one cylinder
- Flashing check engine light
- Loud knocking or hammering from one bank
- Near-zero compression in the affected cylinder
- Complete loss of power / engine barely idles
- Rough running that appears without warning
How to Fix
There is no recall and no free remedy. Diagnose with a compression or leakdown test plus a borescope before spending money on coils and injectors - a dropped seat will not respond to a tune-up. The repair is cylinder head replacement (both heads are usually done together on high-mileage engines, since the other side has the same seats and the same heat history), with valve-to-piston damage often forcing piston or short-block replacement as well. Many owners with 150k+ miles find a used or remanufactured long block is cheaper than a head job plus machine work. Preventively, the single best defense is to treat any overheat, coolant loss or hot-running episode as an emergency and to keep the cooling system - radiator, thermostat, water pump, fan clutch - in good order, because overheating is the documented trigger.
Sources for this issue (3)
The 3.7L SOHC V6 shares its valvetrain architecture with the 4.7 and inherits its worst habit: the stamped rocker arm sits on a hydraulic lash adjuster and is retained only by valve-spring pressure. When the lash adjuster bleeds down or seizes - typically from extended oil-change intervals, low oil level or oil coking - the rocker loses its perch and falls off the valve tip. The engine first develops a light tick at idle, which owners and shops routinely misdiagnose as normal lifter tap, then progresses to a hard tap, a dead cylinder and in the worst Commander cases a rocker that has beaten its way through the valve cover. This is a distinct failure from the 4.7's valve-seat problem, and it does not apply to the 5.7 Hemi, which uses a pushrod valvetrain with a completely different rocker design.
Common Symptoms
- Ticking or tapping from top of engine, worst at idle
- Tick escalating to a hard knock over weeks
- Misfire on one cylinder
- Check engine light
- Cold-start rattle from timing chain area
- Oil leak from a cracked valve cover in extreme cases
How to Fix
Do not dismiss a new tick on a 3.7 as lifter noise. Pull the valve covers early - it is a comparatively cheap inspection - and look for a rocker off its lash adjuster or an adjuster that will not pump up. Caught early the fix is replacing the affected rocker arms and lash adjusters, checking the cam lobe for wear, and correcting the oiling problem that caused it (short oil-change intervals with the correct 5W-30, and verifying the oil pickup and filter are not restricted). Left alone the rocker chews the cam lobe and valve tip, escalating to cylinder head or engine replacement. Related: the same engine family's timing chain tensioner and nylon chain guides wear and produce a cold-start rattle, so inspect the chain and tensioner while the front of the engine is apart on higher-mileage examples. No recall covers either failure.
Sources for this issue (3)
The 4.0L coil-rail ignition system used on TJ Wranglers is known to develop internal failures that cause intermittent or persistent misfires. Owners report rough idle, hesitation, flashing check-engine lights, and cylinder-specific misfire codes, often after moisture intrusion, age, or heat exposure. Because the rail serves all cylinders, diagnosis can be less straightforward than on engines with individual plug wires.
Common Symptoms
- Rough idle
- Engine stumble under load
- Flashing check engine light
- Cylinder-specific misfire codes
- Poor fuel economy
How to Fix
Scan for misfire codes, inspect spark plugs, and verify injector and compression health before condemning the coil rail. If the rail is weak or cracked, replacement of the coil rail assembly and spark plugs is the typical fix. Dielectric grease on the boots and ensuring the valve cover area stays dry can help longevity.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mopar 56041476AB ignition coil railOEMMopar 56041476AB
Replace a test-confirmed weak, cracked or internally failed coil rail Fitment/availability: 2000-2006 Wrangler TJ/LJ with 4.0L inline-six; not 2.4L/2.5L distributor or individual-coil systems. Confirm wiring and paired-cylinder evidence …
- Champion Copper Plus 412 / RC12LYC spark plugOEMChampion 412 / RC12LYC
Replace worn or fouled correct-spec plugs as a set of six after confirming the vehicle's emission-label specification Fitment/availability: 0.035-inch copper plug commonly specified for the 4.0L waste-spark application; quantity six requ…
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P0305 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0305 mean on a Jeep?
P0305 stands for "Cylinder 5 Misfire Detected." This code means the engine control module detected a misfire on cylinder number 5, meaning that cylinder is not burning its air-fuel mixture properly on some combustion cycles. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder fails to fire correctly. A misfire wastes fuel, can make the engine run rough or shake, and dumps unburned fuel into the exhaust, which can overheat and damage the catalytic converter. It generally points to a problem with spark, fuel delivery, or compression specifically affecting cylinder 5. On Jeep it is documented across 3 models: Grand Cherokee, Commander, Wrangler.
What are the most common causes of P0305?
The most common causes of P0305 are: Worn or fouled spark plug on cylinder 5, Failed ignition coil or coil pack for cylinder 5, Faulty or clogged fuel injector on cylinder 5, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire or boot (on applicable engines), Low compression from worn rings, valves, or head gasket, Carbon buildup or sticking valve on cylinder 5, Lean or rich fuel condition affecting the cylinder. The specific cause varies by vehicle.
How much does it cost to fix P0305 on a Jeep?
Published repair estimates on Jeep range from $180 to $7,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0305 on a different make?
View P0305 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.