P0303 on Jeep: How to Diagnose & Fix
Cylinder 3 Misfire Detected
6 Jeep models · 9 documented issues · 6 critical · $100-$7,500 repair
P0303 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 3.7L PowerTech V6 engine suffers from two common issues: cracked exhaust manifolds (causing ticking noise and exhaust leak) and valve cover gasket oil leaks. The cast iron exhaust manifolds develop stress cracks due to thermal cycling, with the passenger side being more common. TSB 09-001-10 addressed valve cover oil leaks. Head gasket failures have also been reported on higher-mileage engines.
Common Symptoms
- Ticking noise from engine on cold start
- Exhaust smell in cabin
- Oil leak on valve covers
- Oil spots on driveway
- Reduced fuel economy
- Check engine light for exhaust leak codes
How to Fix
For exhaust manifold: Replace cracked manifold with new OEM or aftermarket unit ($200-400 per side, $400-800 labor). For valve cover gaskets: Replace both gaskets using Mopar 53021828AB gasket set ($20-40 parts, $200-400 labor). Use Permatex Ultra Grey sealant on the half-moon seals. For head gasket: If coolant mixes with oil, head gasket replacement needed ($1,500-2,500). TSB 09-001-10 provides dealer diagnostic guidelines for oil leaks.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mopar 53013692AB passenger/right exhaust manifoldOEMMopar 53013692AB
Right exhaust-manifold replacement after inspection proves that side is cracked or damaged Fitment/availability: 2005-2012 Jeep Liberty 3.7L, passenger/right side, superseding 53013692AA. Not the left manifold and not approved for 2002-2…
- Genuine Mopar 53013691AC driver/left exhaust manifoldOEMMopar 53013691AC
Left exhaust-manifold replacement after inspection proves that side is cracked or damaged Fitment/availability: 2005-2012 Jeep Liberty 3.7L, driver/left side catalog branch. Not the right manifold and not approved for 2002-2004 without V…
- Genuine Mopar 53013932AB passenger/right exhaust-manifold gasketOEMMopar 53013932AB
Do not substitute for the left gasket.
- Genuine Mopar 53013933AB driver/left exhaust-manifold gasketOEMMopar 53013933AB
Do not substitute for the right gasket.
- Fel-Pro VS50518R valve-cover gasket setOEMFel-Pro VS50518R
Valve-cover gasket replacement after the cleaned engine proves a cover leak on the early 3.7L branch Fitment/availability: 2002-2005 Jeep Liberty 3.7L listing. Confirm exact cover material, included grommets and VIN because 2005 overlaps…
- Fel-Pro VS50652R valve-cover gasket setOEMFel-Pro VS50652R
Both-cover gasket replacement after the cleaned engine proves a cover leak on the later plastic-cover branch Fitment/availability: 2005-2012 Jeep Liberty 3.7L with plastic valve covers and included grommets. Confirm exact cover material/…
- Genuine Mopar 53020989AB 3.7L cylinder-head gasketOEMMopar 53020989AB
Confirm side, full gasket/bolt req
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipThe ticking on cold start that goes away when warm is almost always a cracked exhaust manifold - not lifter noise
Sources for this issue (1)
The 2.4L ED3 head gasket fails between a coolant jacket and a cylinder - cylinder 3 is the most commonly named - pushing coolant into the combustion chamber. Owners describe steady coolant loss with no external puddle, a single-cylinder misfire that survives plug and coil replacement, white sweet-smelling exhaust smoke on start-up, and overheating that appears only under load. The aluminum head warps easily once it has been overheated, so a head-gasket job that skips a straightedge check fails again. This failure is repeatedly reported on the 2.4L and should not be assumed for the 2.0L, which is a lower-output, lower-stress version of the same architecture.
Common Symptoms
- Coolant disappearing with no visible external leak
- White smoke from the exhaust on start-up
- Single-cylinder misfire that returns after new plugs and coils
- Overheating under load
- Bubbles in the coolant reservoir
- Milky residue under the oil cap
How to Fix
Confirm before tearing down: a block test (combustion-gas detector) on the coolant, a cooling-system pressure test and a cylinder leak-down test together will separate a head gasket from a cracked head. Repair means removing the head, machining or replacing it if it is out of flat, a new MLS gasket and new head bolts (torque-to-yield, never reuse), plus plugs and any coil fouled by coolant. Shop cost typically $1,500-$2,600. No recall or FCA extended warranty covers this failure.
Sources for this issue (3)
The Pentastar's variable valve lift followers use a roller only on the low-lift portion; the high-lift pad slides directly on the cam lobe. When the needle bearings in the rocker arm fail or the sliding pad wears, the follower cuts a groove into the intake camshaft lobe, valve lift drops and the cylinder misfires. Owners report a light tick appearing within a few thousand miles of a service interval that grows into a loud diesel-like clatter by 10,000-20,000 miles, often followed by a check engine light. Left alone, the wearing lobe and bearing cage shed metal through the oil system.
Common Symptoms
- Ticking or tapping from the top of the engine, loudest at idle
- Noise worsening over thousands of miles into a diesel-like clatter
- Check engine light with single-cylinder or random misfire
- Rough idle
- Metal flake in the oil filter
How to Fix
Diagnose early: cylinder-specific misfire plus a cold tick that persists warm points at the rocker/cam. The proper repair is replacement of the failed rocker arms AND the worn camshaft (replacing rockers alone on a grooved lobe fails again), plus an oil and filter change to purge debris. Covered under the 5yr/60k powertrain warranty on many trucks; extended coverage has been granted case by case. Sticking to the correct oil spec and not extending oil change intervals reduces risk.
Sources for this issue (4)
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)
P0303 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 P0303 mean on a Jeep?
P0303 stands for "Cylinder 3 Misfire Detected." This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. On Jeep it is documented across 6 models: Grand Cherokee, Liberty, Patriot, Gladiator, Commander, Wrangler.
What are the most common causes of P0303?
The most common causes of P0303 are: Worn or fouled spark plug in cylinder 3, Failed or weak ignition coil on cylinder 3, Bad spark plug wire or boot (where applicable), Clogged or leaking fuel injector for cylinder 3, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket), Wiring or connector fault at the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0303 on a Jeep?
Published repair estimates on Jeep range from $100 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 P0303 on a different make?
View P0303 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.