If the warning light is flashing, reduce speed and stop driving as soon as it is safe. Continued running can destroy the catalytic converter, which is an expensive repair on top of whatever caused the misfire. A steady light with rough running still needs prompt attention.
The engine control module counts crankshaft acceleration between firing events. When combustion fails often enough, and the fault wanders across cylinders rather than settling on one, it stores P0300 instead of a cylinder-specific code. That distinction matters: a random misfire points at something the whole engine shares — fuel supply, air metering, ignition timing, compression across the board — rather than one failed coil or plug. Unburnt fuel reaching a hot catalytic converter is what makes this urgent; a flashing warning lamp means damage is happening now, not eventually.
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
A random-misfire code with no P0301–P0306 alongside it means the misfires are spread across cylinders, and that changes the suspect list completely. One cylinder misfiring is that...
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