Cylinder 3 Misfire Detected
Indicates a misfire has been detected in cylinder 3.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine control module (ECM) is noticing that cylinder 3 is not firing properly, which can lead to rough running and higher emissions.
What the computer is actually seeing
The ECM monitors the crankshaft position and ignition timing. If it sees a change in engine RPM that doesn't match expected values while cylinder 3's injector and coil are operating normally, it registers a misfire.
What a healthy reading looks like
Expected RPM fluctuation should be less than 2% for all cylinders; misfires and engine RPM should stay within 600-700 RPM while idling.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Check for any other active trouble codes.
- 2Inspect the wiring and connectors for the ignition coil and fuel injector in cylinder 3 for damage or corrosion.
- 3Test the spark plug in cylinder 3 for wear or damage; replace if necessary and recheck.
- 4Swap ignition coils with another cylinder (e.g., cylinder 1); clear codes and road test. If P0303 returns, the coil is okay.
- 5Perform a fuel injector balance test. If cylinder 3 shows low fuel delivery, replace the injector and test again.
- 6Use a mechanical gauge to check cylinder compression; values should be within 10% of each other across all cylinders.
Common causes
- Faulty spark plug in cylinder 3
- Faulty ignition coil for cylinder 3
- Fuel injector issues for cylinder 3
- Vacuum leaks affecting cylinder 3
- Low compression in cylinder 3
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable, but it may cause poor fuel economy and higher emissions. Fix soon to prevent further damage.
Will this code come back after clearing it?
If the underlying issue isn't resolved, yes, the code will likely return.
Why does this code pair with P0300?
P0300 is a random/multiple cylinder misfire code. If multiple cylinders misfire, it's usually due to a common issue affecting spark, fuel, or air supply.
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