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A check engine light or malfunction indicator lamp (MIL), is a tell-tale that a computerized engine-management system used to indicate a malfunction or problem with the vehicle ranging from minor (such as a loose gas cap) to serious (worn spark plugs, engine problems or a faulty oil valve, etc.). Found on the instrument panel of most automobiles, it usually bears the legend engine,[1] check engine, service engine soon, maintenance required, emiss maint,[2] or a pictogram of an engine—and when illuminated, it is typically an amber or red color.
The light generally[3] has two stages: steady (indicating a minor repairable fault, but service on the vehicle is strongly recommended as soon as possible to prevent future damage) and flashing (indicating a severe fault and an emergency that makes the vehicle unsafe to drive and it is strongly recommended that the vehicle gets mechanical attention straight away). When the MIL is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved—although in many models this requires the use of a scan tool. This warning light can indicate almost anything from a loose gas cap to a serious knock or fault in the engine.[4]
In the United States, specific functions are required of the MIL by EPA regulations.[5]
- ^ 1980s and 1990s Ford F-Series trucks had an optional "redundant engine light", a second engine light alongside the check engine light, which would only light under severe conditions. As the name suggests, its purpose was redundancy in case the primary MIL failed.
- ^ "Check Engine Light".
- ^ On vehicles equipped with OBD-II
- ^ "Diagnose service engine soon light fix with this professional car diagnostic tool". Key Smiths. April 11, 2018. Retrieved April 11, 2018.
- ^ Register, Office of the Federal. Code of Federal Regulations, Title 40, Protection of Environment, PT. PT. 85-86 (SEC. 86.599-99), Revised as of July 1, 2010. Government Printing Office. ISBN 978-0-16-086040-9.