P0303 on FORD MUSTANG — Cylinder 3 Misfire Detected

Q: "What does P0303 mean on a FORD MUSTANG?"

"P0303 indicates: Cylinder 3 Misfire Detected. This is a ignition system code. 3 FORD MUSTANG owners have reported this to NHTSA."

Q: "What are the most common causes of P0303 on FORD MUSTANG?"

"Based on 3 NHTSA reports, the most commonly cited components are: Engine, Power Train,Engine. These percentages are based on the component field in owner complaints."

Q: "Is P0303 serious on my FORD MUSTANG?"

"Of 3 NHTSA reports for this code on FORD MUSTANG, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic."

Q: "What should I do if my FORD MUSTANG shows P0303?"

"1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare."

What P0303 Means on Your FORD MUSTANG

P0303 is a diagnostic trouble code indicating: Cylinder 3 Misfire Detected. This code relates to the ignition system system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

3 FORD MUSTANG owners have reported this issue to NHTSA across model years 2016-2018. Most reports come from the 2018, 2016 model years. The most commonly reported component is Engine (66.7% of reports).

Real FORD MUSTANG Owner Reports

Source: NHTSA Complaints Database

"My car started to show a check engine light on around 103,000 miles. After getting a check engine light reading, the code was a misfire p0303 on cylinder 3. I took the car to a mechanic and was told the head gasket was blown and coolant was leaking into it."

— 2016 FORD MUSTANG owner · ENGINE · Filed 08/18/2023

"Random/multiple misfires and cyl 3 misfire (P0300 and P0303). Mechanic used a borescope and found coolant on the walls; visible coolant intrusion in cylinder 3. Coolant has gotten to low levels. Very rough cold start. Mechanic highly recommends to get the engine replaced."

— 2018 FORD MUSTANG owner · ENGINE · Filed 01/08/2026

"For roughly 4mths beginning in April 2025, my 2018 Ford Mustang Ecoboost has been suffering from a sporadic misfire, with it the system reporting the misfire and the check engine light coming on, the Ford App identifying the misfire occurring."

— 2018 FORD MUSTANG owner · POWER TRAIN,ENGINE · Filed 04/25/2025

All reports filed by vehicle owners directly with the U.S. Department of Transportation.

📊 Complaint Trend by Model Year

1

'16

2

'18

Common Causes on FORD MUSTANG

Based on NHTSA complaint component analysis for this vehicle.

ENGINE 66.7%

POWER TRAIN,ENGINE 33.3%

What To Do Next

1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.

Frequently Asked Questions

What does P0303 mean on a FORD MUSTANG? ▾

P0303 indicates: Cylinder 3 Misfire Detected. This is a ignition system code. 3 FORD MUSTANG owners have reported this to NHTSA.

What are the most common causes of P0303 on FORD MUSTANG? ▾

Based on 3 NHTSA reports, the most commonly cited components are: Engine, Power Train,Engine. These percentages are based on the component field in owner complaints.

Is P0303 serious on my FORD MUSTANG? ▾

Of 3 NHTSA reports for this code on FORD MUSTANG, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic.

What should I do if my FORD MUSTANG shows P0303? ▾

1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare.