In order to find the remedy, you first need to know the cause. On this vehicle, the P0300 code indicates a misfire in one or more of the cylinders of the engine. In the majority of cases, this can be traced to a faulty coil, high-tension lead, spark plug, computer or even the fuel system. The warning shows that one of the cylinders is not firing as cleanly as it should be, so those are the basic thigs to start with. The problem could be as simple as moisture inside one of the coils or its fittings, or even a simple dodgy spark plug. If that’s the case, replace all of them, rather than just the one that’s faulty, as the rest are also likely to be getting towards the end of their life.