P0303
Cylinder 3 Misfire Detected
Quick answer: P0303 means cylinder 3 Misfire Detected. Fixing the underlying cause typically runs $195 to $1,150 at an independent shop. Get it checked promptly.
- Severity
- High
- Safe to drive?
- Get it checked promptly
- Typical repair
- $195 to $1,150
- Most likely cause
- A failed ignition coil on cylinder 3 (the most common cause by a wide margin)
What P0303 means
The computer detected repeated misfires and traced them to cylinder 3, which points at the coil, spark plug, or injector serving that one cylinder. A single-cylinder code like this is one of the more diagnosable problems a car can have, since a mechanic can move parts between cylinders and watch whether the misfire moves too. On some V6 engines cylinder 3 sits on the bank tucked against the firewall, which does not change the diagnosis but can add labor to reach it.
Common symptoms
What drivers usually notice with this code.
- Rough, shaky idle you can feel through the seat or steering wheel
- Check-engine light flashing during acceleration
- Hesitation and reduced power, most obvious when merging or climbing
- Worse fuel economy and sometimes a fuel smell from the tailpipe
- Smoother running at speed than at idle
Common causes
Ranked from most to least likely.
- 1A failed ignition coil on cylinder 3 (the most common cause by a wide margin)
- 2A worn, fouled, or cracked spark plug in cylinder 3
- 3A clogged or leaking fuel injector on cylinder 3
- 4A damaged wire or corroded connector at the cylinder 3 coil
- 5A vacuum leak at that cylinder's intake port or a torn intake gasket
- 6Low compression in cylinder 3 from a burnt exhaust valve or worn rings
Can I keep driving?
With a steady light, drive gently and get it looked at within a day or two; with a flashing light, the misfire is actively cooking your catalytic converter, so pull over and get a tow.
Severity: High. A flashing check-engine light always means stop, whatever the code says.
Ballpark cost
What P0303 usually costs to fix
A range, not a quote. What you pay depends on your vehicle, your area, and which of the causes above turns out to be the real one.
Typical parts and labor at an independent shop. Dealer rates run higher.
That spread is wide on purpose. P0303 points at a system, not a single part, so the real answer depends on what the diagnosis finds. Use the range to know what to expect. If an estimate comes in higher, it usually means the specific repair is more involved, and it is always fair to ask what is included.
Next steps
What to do next
The standard play is a coil-and-plug swap test: move cylinder 3's coil and plug to another cylinder, clear the code, and see whether the misfire follows. If it does, you are looking at an inexpensive ignition repair; if it stays on cylinder 3, ask for a compression or leak-down test before approving anything major. On engines where cylinder 3 is on the rear bank, ask up front how much of the quote is access labor, so the numbers make sense to you.
Walk in informed
Ask for the diagnosis in writing and which test confirmed it, so you understand exactly what is being fixed. Fixxr shows you what the job typically costs near you, so you can approve the work with confidence.
Sources & further reading
- NHTSA — Check for vehicle safety recalls — look up open recalls for your vehicle by VIN, free
- FTC — Auto repair basics — your consumer rights at the repair shop
- AAA — Car repair and maintenance costs — independent guidance on what repairs should cost
Cost ranges and guidance reviewed July 2026.
P0303 FAQ
P0303 questions, answered
Can I drive with a P0303 code?
With a steady light, drive gently and get it looked at within a day or two; with a flashing light, the misfire is actively cooking your catalytic converter, so pull over and get a tow.What does the P0303 code mean?
The computer detected repeated misfires and traced them to cylinder 3, which points at the coil, spark plug, or injector serving that one cylinder. A single-cylinder code like this is one of the more diagnosable problems a car can have, since a mechanic can move parts between cylinders and watch whether the misfire moves too. On some V6 engines cylinder 3 sits on the bank tucked against the firewall, which does not change the diagnosis but can add labor to reach it.What are the most common causes of a P0303 code?
The most likely causes, roughly in order, are a failed ignition coil on cylinder 3 (the most common cause by a wide margin); a worn, fouled, or cracked spark plug in cylinder 3; a clogged or leaking fuel injector on cylinder 3; a damaged wire or corroded connector at the cylinder 3 coil. The standard play is a coil-and-plug swap test: move cylinder 3's coil and plug to another cylinder, clear the code, and see whether the misfire follows. If it does, you are looking at an inexpensive ignition repair; if it stays on cylinder 3, ask for a compression or leak-down test before approving anything major. On engines where cylinder 3 is on the rear bank, ask up front how much of the quote is access labor, so the numbers make sense to you.How much does it cost to fix a P0303 code?
Fixing the underlying problem behind a P0303 code typically runs $195 to $1,150 at an independent shop, including parts and labor. The exact figure depends on your vehicle and which part turns out to be at fault.
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