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.
Circuit Description
The DTC P0300 Engine Misfire Detected diagnostic illuminates Malfunction Indicator Light (MIL) when a Not Cylinder Specific misfire is present. Powertrain Control Module (PCM) uses Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor to determine engine misfire. CKP and CMP sensors monitor their respective components and evaluate changes in crankshaft rotational speed for each cylinder. Irregular changes in crankshaft rotational speed indicate a possible misfire. MIL illuminates when misfire rate equals or exceeds a pre-determined count. A misfire rate that is high enough can cause catalytic converter to overheat under certain driving conditions. MIL will flash ON and OFF when conditions for catalytic converter overheating are present. Each cylinder is monitored individually for a misfire condition. A DTC P0300 indicates engine misfire was indicated in more than one cylinder at the same time.
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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.