A driver can continue operating a vehicle if the check engine light comes on and stays on, but the vehicle does not have any noticeable problems. A flashing check engine light indicates a more serious problem, and the driver should immediately pull over.
The check engine light may come on intermittently. The vehicle's computer retains a history code that a mechanic can retrieve and assess even if the check engine light is no longer on.
The check engine light may come on if the vehicle has a broken or loose hose, experiences engine misfire or has a problem with an air flow or temperature sensor. Lack of recommended maintenance can cause vehicle systems to work improperly, also causing the check engine light to come on.