P0303: Cylinder 3 Misfire Detected
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Short careful trips only, and only while the check engine light is steady. A FLASHING light means stop - raw fuel is overheating the catalytic converter, and a glowing converter is a fire risk.
Symptoms
- Flashing check engine light
- Rough idle, vibration through the seat
- Hesitation on acceleration
Likely causes, most common first
- Worn spark plug or failing coil on cylinder 3
- Injector fouling
- Intake gasket leak near that runner
- Low compression
Read P0303 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0303 points at cylinder 3. On transverse V6 engines - the layout in most front-wheel-drive sedans and minivans - the odd-numbered bank often sits at the back, against the firewall, and reaching its plugs and coils can mean removing the intake manifold. That single fact explains why the same misfire costs twice as much on one cylinder as on another.
Before committing to that labour, confirm the fault actually lives in cylinder 3. Swapping the coil to a front-bank cylinder and rechecking is free; if the misfire moves with the coil, you never had to touch the back of the engine at all.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0303
“vehicle may experience driveability issues, which may result in DTCs P0300 (random misfire detected), P0301 (No. 1 cylinder misfire detected), P0302 (No. 2 cylinder misfire detected), P0303 (No. 3 cylinder misfire detected), P0304 (No. 4 cylinder misfire detected), or P0172 (fuel system too rich) or a whirling noise coming from the engine compartment. POSSIBLE CAUSE Based on certain driving patterns and environmental factors, the DTC's stated above may be set or a whirling noise may occur. Apparently only certain vin numbers were affected, mine is not in the list but im still having the exact same issues.”2017 Honda CR-V · Aug 2026
“Failed head gasket that put vehicle in compromised working condition on the roadway - check engine light flash, poor and inconsistent engine running. First indications were 5-10 seconds of rough idle after startup when sitting overnight, then p0303 check engine code for cylinder three misfire as well as loss of coolant. Independent shop confirmed issue and replaced head gasket. Problem appears to have re-occurred after 2 years and 20000 miles with similar indications. Same shop advised likely engine block or cylinder head defect or damage and would not do any tear down or repair short of engine replacement.”2018 Chrysler Pacifica · Aug 2026
“Engine is misfiring due to coolant intrusion leak issue. The only solution is full engine replacement. A check engine light with code P0303 was shown. The car occasionally runs rough and coolant was observed to be low.”2017 Ford Edge · Aug 2026
Show 7 more owner reports
“The contact owns a 2018 Ford Edge. The contact stated that an independent mechanic became aware that coolant was leaking into cylinder #3. The check engine warning light was illuminated. Additionally, DTC: P0303 was displayed. The contact associated the failure with NHTSA Action Number: DP26008 (Engine and Engine Cooling). The dealer was contacted. The manufacturer was contacted by phone and made aware of the failure. The failure mileage was approximately 114,700.”2018 Ford Edge · Jul 2026 · 114,700 mi
“Coolant leaking into cylinder confirmed by independent mechanic. Unable to clear code P0303. This is a documented problem with this make model with eco-boost engines but Ford claims my car is not included in recall although i do have the eco-boost and make model and year. Need complete engine replace. This is a major engine design problem”2017 Ford Escape · Jul 2026
“The vehicle in question has the coolant intrusion into cylinders 2 and 3 with rough idle on startup, P0300, P0302, P0303, and white smoke on startup. The vehicle now has 111339 miles on it and the out of pocket cost is more than what the vehicle blue books for in excellent condition. TSB 22-2134 speaks to all the issue and what the repair is. If this is a known issue then I feel this should be a vehicle recall by Ford due to the costly repair.”2017 Ford Fusion · Jul 2026
“I experienced rough idle and smell of coolant at start up. Engine light came on. Took car to dealership for diagnosis. Dealer verified my concern ran pcm self test, p0300, p0302 p0303 p0316 present, found coolant intrusion into cylinders. Dealer replaced long block per wsm 303-01. Cost to me $8,036.29. My 2017 Edge had 72,177 miles.”2017 Ford Edge · Jul 2026
“The engine overheated and went into limp mode while on the busy interstate, we nearly were hit trying to get off the road because we could not keep speed. The car is available for inspection. It has the typical symptoms of the coolant intrusion as acknowledged by Ford in Technical Service Bulletins 19-2139 and 22-2322. These include startup misfires, rapid loss of coolant into the combustion chambers without external leaks, and severe overheating causing the vehicle to enter limp mode. The misfire's are throwing engine codes P0302 (Cylinder 2 Misfire Detected) and P0303 (Cylinder 3 Misfire Detected) This just happened on July 8, 2026 and the car has 105,203 miles.”2017 Ford Escape · Jul 2026
“Started (first noticed)check engine light flashing turned radio down right of way and noticed engine knocking with no warning still 40% engine oil life left. Had test done P0303 misfire on cylinder 3 and rod bearing knock was told need an engine . Had all oil changes and maintenance done on time. ran my vin and unfortunately was told it is not covered under recall.”2016 Acura MDX · Jun 2026
“Head cracked and allowed coolant to intrude into the cylinders causing misfiring and white smoke to come out of the exhaust. Barely made it off the highway to a safe location as I was quickly loosing acceleration. Issue confirmed by Sames Ford dealership in Harlingen, TX (codes p0302 and p0303). They informed me that this is a known issue with this 1.5L Ecoboost motor in this vehicle. Vehicle is a total loss and I still owe a significant amount on the lease.”2018 Ford Escape · Jun 2026
Cars that report P0303 most often
Based on mentions of this code in NHTSA owner complaints.
P0303 by make
Makes with enough NHTSA reports of P0303 for a page of their own - which models and years report it.
Frequently asked questions
Can I drive with P0303?
Short careful trips only, and only while the check engine light is steady. A FLASHING light means stop - raw fuel is overheating the catalytic converter, and a glowing converter is a fire risk.
How much does it cost to fix P0303?
Typical US repair costs range from $20 for the simplest fix (spark plug) to $700 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0303. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.