Malfunction Indicator Lamp: Description and Operation

The Electronic Control Assembly (ECA) transmits the "CHECK ENGINE" message to the message center through the Data Communications Link (DCL). The message center is used to display the "CHECK ENGINE" and/or "CHECK DCL" messages. During self test the message center can also be used to display the service codes.
The "CHECK ENGINE" message is activated when the ECA switches to an alternate strategy of operation. This process is called Failure Modes Effect Management (FMEM). The "CHECK ENGINE" message is intended to alert the driver of certain malfunctions in the Electronic Engine Control (EEC-IV) system. When the vehicle enters FMEM the "CHECK ENGINE" message will be displayed and accompanied by a one second tone every five seconds. The tone will be suppressed after one minute.
The "CHECK ENGINE" message will also be displayed during a period of Hardware Limited Operating Strategy (HLOS) operation. In addition to the "CHECK ENGINE" message and tone, the message "CHECK DCL" will also be displayed.