To check if your spark plug is working properly, you need to first unscrew it from the engine. Once removed, inspect the ceramic body for signs of cracking or damage. If damaged, replace the spark plug with a new one. Additionally, make sure that there is no debris such as dirt or oil on the threads of the spark plug. Next, use an ohmmeter to test resistance on both sides of the central electrode. Generally speaking, acceptable readings range between 5 and 10k ohms at room temperature. If resistance falls outside these parameters or reads “OL” (open loop), then it's time to replace your spark plug with a new one. Lastly, you can also visually inspect ignition cables connected to each end of the spark plugs for any signs of corrosion or wear which could be causing misfiring issues in your engine's cylinders. By carrying out this simple maintenance task periodically, you can ensure that your vehicle's performance remains optimal and free from costly repairs down the line!