Answer: Engine diagnostics keep your engine running efficiently. The OBD-II System can detect problems before they damage your engine or hurt its performance. These diagnostics will detect problems and turn on your “check engine” light. If your “check engine” light stays on, you have a problem with your engine, and it should be checked. These diagnostics will let you take care of problems early and help you save money. The diagnostics will also keep your vehicle running efficiently and keep your vehicle’s emissions low. If you ignore your “check engine” light, you can be damaging your engine. Also, your vehicle may not pass emissions tests when this light is on.