| The check engine light is illuminated | The engine or transmission computer has detected a fault that requires code retrieval and diagnosis. |
| The ABS or traction-control light is on | The vehicle may have detected a problem involving wheel-speed sensors, wiring, hydraulic controls, or another connected system. |
| The airbag warning light stays on | The supplemental restraint system may have stored a fault and one or more safety features may be unavailable. |
| Multiple warning lights appear together | The systems may share a sensor, electrical supply, communication network, or related fault. |
| A vehicle feature stops working | A sensor, switch, control module, actuator, wiring circuit, or communication problem may be involved. |
| The vehicle behaves intermittently | An electrical connection, sensor signal, module, or network issue may be occurring only under certain conditions. |
| The battery repeatedly loses charge | A charging-system, electrical draw, wiring, module, or battery-related concern may require testing. |
| A warning returns after being cleared | The underlying fault may still be present and needs to be properly diagnosed. |