There is a 2017 Toyota Highlander ignition coil connected to each of your spark plugs, and it's responsible for increasing the voltage in electrical current before so it can be used by the plugs. Signs that your coils may be going bad include lessened acceleration, trouble starting, a lit Check Engine Light, and lower MPG. We carry a variety of 2017 Highlander ignition coils from trusted brands, so you can choose the ones that meet your needs.