You need to take the car to a mechanic who will be able to scan the vehicle to see if the on-board computer has noticed anything amiss and logged it for future reference. This should be a quick process and shouldn’t cost much, but without talking to the computer you won’t have all the information you need to make an informed diagnosis and subsequently tackle the problem.

For the record, the cause could be within the fuel system, the ignition system or something mechanical with the way the throttle body is set-up or adjusted. This model was also pretty well known for crank-angle sensor failure which, in its early phases, could be part of the problem here.

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.

Parts and service supply has been a bit of an ongoing problem for some owners of these earlier Chinese-made Great Wall commercial vehicles. Some were sidelined for extended periods after some service parts were hard to locate and it’s doubtful that Covid and its attendant supply-chain problems have helped in that regard.

I’m a bit surprised, however, to learn that a Great Wall dealership lacks the tools and techniques necessary to carry out just about any maintenance task, including electrical jobs. Perhaps a call to Great Wall’s Australian customer service number might do the trick. If your nearest dealers don’t have the necessary equipment, perhaps there’s another dealer a little farther away that does. Failing that, try one of the many online forums for a solution. Chances are your vehicle won’t be the only one with this specific problem, and other owners may be able to offer advice on who can carry out the work.