# Check engine light > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Check_engine_light > Markdown URL: https://mediated.wiki/source/Check_engine_light.md > Source: https://en.wikipedia.org/wiki/Check_engine_light > Source revision: 1352490619 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Type of indicator light in automobiles The examples and perspective in this article may not represent a worldwide view of the subject. You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. (October 2007) (Learn how and when to remove this message) *Check engine icon*, also known as the *malfunction indicator icon* A check engine light labeled "service engine soon" A check engine light on a Volkswagen Bora indicating a fault in the engine management system Check engine light on a running engine indicating malfunction in engine control system A **check engine light** or **malfunction indicator light** (**MIL**) or **lamp**, is a [tell-tale](/source/Tell-tale_(automotive)) that a computerized engine-management system uses 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,[a] check engine, service engine soon, maintenance required, emiss maint,[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] or a pictogram of an engine—and when illuminated, it is typically an amber or red color. The light generally[b] 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 check engine light is lit, the [engine control unit](/source/Engine_control_unit) stores a fault code related to the malfunction, which can be retrieved—which usually requires the use of a [scan tool](/source/On-board_diagnostics#Hand-held_scan_tools). This warning light can indicate almost anything from a loose gas cap to a serious knock or fault in the engine.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] In the United States, specific functions are required of the check engine light by [EPA](/source/United_States_Environmental_Protection_Agency) regulations.[1] ## History Some older vehicles had a single indicator labeled "trouble" or "engine"; this was not a check engine light, but a tell-tale meant to indicate serious trouble with the engine (low oil pressure, overheating, or charging system problems) and an imminent breakdown. This usage of the "engine" light was discontinued in the mid-1980s, to prevent confusion with the check engine light.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] The check engine light appeared in the early 80s along with computerized engine controls. Even the earliest systems, such as [General Motors](/source/General_Motors)' CCC (computer command control) system had self diagnosis functionality. When the computer detected a fault, it illuminated the check engine light. Up until [OBDII](/source/On-board_diagnostics#OBD-II), on most cars the check engine light could output codes. When two pins on the [ALDL](/source/ALDL) are jumped, the light would flash the codes, for instance (blink) (pause) (blink) (blink) for code 12. Some manufacturers, such as Honda, retained this feature even after OBDII.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] The check engine light is commonly referred to today as the "check engine light" or the "service engine soon light".[2][3] ## See also - [OBD-II PIDs](/source/OBD-II_PIDs) – Codes used for on-board diagnostics ## Notes 1. **[^](#cite_ref-1)** 1980s and 1990s [Ford F-Series](/source/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 check engine light failed.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] 1. **[^](#cite_ref-2)** On vehicles equipped with [OBD-II](/source/On-Board_Diagnostics)[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] ## References 1. **[^](#cite_ref-3)** [Code of Federal Regulations, Title 40, Protection of Environment, PT. 85–86 (SEC. 86.599–99)](https://books.google.com/books?id=q8_vHlaJHVwC&dq=Malfunction+indicator+light+OBD&pg=PA200). Government Printing Office. July 1, 2010. [ISBN](/source/ISBN_(identifier)) [978-0-16-086040-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-16-086040-9). 40 CFR 85–86 § 86.599–99. Retrieved October 7, 2010. 1. **[^](#cite_ref-4)** ["How Do the Engines Breathe in Diesel Submarines?"](http://science.howstuffworks.com/transport/engines-equipment/question286.htm). *[HowStuffWorks](/source/HowStuffWorks)*. July 24, 2006. Retrieved October 27, 2016. 1. **[^](#cite_ref-5)** ["Why Does My Car Stall While I'm Driving?"](http://desertoasisautorepair.com/my-car-stalls/). *DesertOasisAutoRepair.com*. Desert Oasis European Auto Service & Repair. Retrieved March 25, 2026. v t e Car interior Part of a series of articles on cars Instruments Automotive navigation system Automotive night vision Backup camera Blind spot monitor Boost gauge Buzzer Carputer Check engine light Electronic instrument cluster Fuel gauge Head-up display Odometer Parking sensor Radar detector Speedometer Tachometer Telematics Tell-tale Trip computer Controls Bowden cable Brake Clutch Cruise control Electronic throttle control Gear stick Manettino dial Parking brake Power steering Steering wheel Anti-theft Alarm Automatic vehicle location Immobiliser Power door locks Remote keyless system Smart key VIN etching Safety Seating Airbag Armrest Bench seat Bucket seat Child safety lock Rearview mirror Rumble seat Seat belt Other elements Boot liner Center console Dashboard Glove compartment Molded carpet Sun visor Vehicle mat Convenience Audio Automobile auxiliary power outlet Cup holder Car phone Category Commons Portal --- Adapted from the Wikipedia article [Check engine light](https://en.wikipedia.org/wiki/Check_engine_light) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Check_engine_light?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.