Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0301 - P0309: Cylinder X Misfire Detected
2010 Ford Focus S, StandardSECTION DTC P0301 - P0309: Cylinder X Misfire Detected
DTC P030X: CYLINDER X MISFIRE DETECTED
| Description: |
NOTE:
x represents cylinder numbers 1 through 9.
The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. |
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| Possible Causes: |
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| Diagnostic Aids: | The malfunction indicator lamp (MIL) blinks once per second when a misfire severe enough to cause catalyst damage is detected. If the MIL is on steady state due to a misfire, this indicates the threshold for emissions was exceeded and caused the vehicle to fail an inspection and maintenance tailpipe test. | ||
| Application | Key On Engine Off | Key On Engine Running | Continuous Memory |
| All | - | - | GO to PINPOINT TEST HD . |
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.