Many break downs and unscheduled repairs are caused by electronic component failure
. A majority of the electronic components prone to failure are associated with the elaborate emission control systems mandated by the US government. The computer that operates and monitors these systems is called the engine control module (ECM). The ECM may monitor as many as twenty-five to thirty different sensors. Whenever a sensor reads out of its preset range, an error code is set by the ECM. This causes the malfunction indicator lamp (MIL), also known as the "check engine light", to illuminate. A technician uses a diagnostic computer to read and interpret the error codes. Many times the repair is as simple and relatively inexpensive as replacing a sensor. Early detection and repair of any problem is essential to the engine's longevity. Never leave the MIL illuminated for extended periods of time because of a minor problem. If a major malfunction should occur with the MIL already illuminated, its first indication may be a breakdown at the most inconvenient time possible. With proper care and maintenance, an engine should provide reliable service for more than three hundred thousand miles.