Cutlass Supreme V6-204 3.4L DOHC VIN X SFI (1995)
Malfunction Indicator Lamp: Description and Operation
DESCRIPTION
The Malfunction Indicator Lamp (MIL) (Service Engine Soon / Check Engine) lamp is on the instrument panel and has the following functions:
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It informs the driver that a problem has occurred and that the vehicle should be taken for service as soon as reasonably possible.
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Some applications will flash diagnostic trouble codes stored by the PCM which help the technician diagnose system problems.
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Some applications will flash "Open Loop" or "Closed Loop" operation.
Refer to Computers and Controls / Testing and Inspection / Vehicle On-Board Diagnostics / Without Scan Tool for information on identifying
exactly what information the MIL can provide. See: Testing and Inspection
As a bulb and system check, the MIL (Service Engine Soon / Check Engine) will come "ON" with the key "ON" and the engine not running. When
the engine is started, the lamp will turn "OFF." If the lamp remains "ON," the self-diagnostic system has detected a problem. If the problem goes
away, the lamp will go out in most cases but a diagnostic trouble code will remain stored.
When the light remains "ON" while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, an
On-Board Diagnostic System Check must be performed. The procedures for these checks is located at Computers and Controls / System
Diagnosis / Flow of Diagnosis. See: Testing and Inspection
These checks will expose malfunctions which may not be detected if other diagnostics are performed prematurely.
