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Malfunction Indicator Icon
A Malfunction Indicator Lamp, this one labeled "Service Engine Soon".
A MIL "Check Engine" light on a Volkswagen Bora indicating a fault in the Engine Management System.
MIL on a running engine indicating malfunction in engine control system.

A malfunction indicator lamp (MIL), also known as a check engine light, is a tell-tale to indicate malfunction of a computerized engine management system. It is found on the instrument panel of most automobiles. When illuminated, it is typically either an amber or red color. On vehicles equipped with OBD-II, the light has two stages: steady (indicating a minor fault such as a loose gas cap or failing oxygen sensor) and flashing (indicating a severe fault, that could potentially damage the catalytic converter if left uncorrected for an extended period). When the MIL is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved with a scan tool and used for further diagnosis, the diagnosis maybe retrieved without a scan tool in some car models. The malfunction indicator lamp usually bears the legend check engine, service engine soon, or a pictogram of an engine. In the United States, specific functions are required of the MIL by EPA regulations.<ref>http://books.google.com/books?id=q8_vHlaJHVwC&pg=PA200&dq=Malfunction+indicator+light+OBD&hl=en&ei=h4j-TNSEFoiDOpaCvc4M&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC0Q6AEwAA#v=onepage&q=Malfunction%20indicator%20light%20OBD&f=false Code of Federal Regulations CFR 40 ar{Part 86, retrieved 2010 Dec 7</ref>

The MIL appeared in the early 80s along with computerized engine controls. Even the earliest systems, such as GM's CCC (Computer Command Control) system had self diagnosis functionality. When the computer detected a fault, it illuminated the MIL. Up until OBDII, on most cars the MIL could output codes, when two pins on the 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.


Check engine light sections
Intro  \"Trouble\" indicator  Odometer triggering  False triggering  See also  References  

PREVIOUS: IntroNEXT: \"Trouble\" indicator
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Engine::light    System::fault    Vehicles::oxygen    Start::check    Engine::thumb    Service::after

{{#invoke:Message box|ambox}}

Malfunction Indicator Icon
A Malfunction Indicator Lamp, this one labeled "Service Engine Soon".
A MIL "Check Engine" light on a Volkswagen Bora indicating a fault in the Engine Management System.
MIL on a running engine indicating malfunction in engine control system.

A malfunction indicator lamp (MIL), also known as a check engine light, is a tell-tale to indicate malfunction of a computerized engine management system. It is found on the instrument panel of most automobiles. When illuminated, it is typically either an amber or red color. On vehicles equipped with OBD-II, the light has two stages: steady (indicating a minor fault such as a loose gas cap or failing oxygen sensor) and flashing (indicating a severe fault, that could potentially damage the catalytic converter if left uncorrected for an extended period). When the MIL is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved with a scan tool and used for further diagnosis, the diagnosis maybe retrieved without a scan tool in some car models. The malfunction indicator lamp usually bears the legend check engine, service engine soon, or a pictogram of an engine. In the United States, specific functions are required of the MIL by EPA regulations.<ref>http://books.google.com/books?id=q8_vHlaJHVwC&pg=PA200&dq=Malfunction+indicator+light+OBD&hl=en&ei=h4j-TNSEFoiDOpaCvc4M&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC0Q6AEwAA#v=onepage&q=Malfunction%20indicator%20light%20OBD&f=false Code of Federal Regulations CFR 40 ar{Part 86, retrieved 2010 Dec 7</ref>

The MIL appeared in the early 80s along with computerized engine controls. Even the earliest systems, such as GM's CCC (Computer Command Control) system had self diagnosis functionality. When the computer detected a fault, it illuminated the MIL. Up until OBDII, on most cars the MIL could output codes, when two pins on the 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.


Check engine light sections
Intro  \"Trouble\" indicator  Odometer triggering  False triggering  See also  References  

PREVIOUS: IntroNEXT: \"Trouble\" indicator
<<>>