Metro L3-61 1.0L (1990)
Malfunction Indicator Lamp: Description and Operation
This light 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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It displays "Trouble Codes" stored by the ECM which help the technician diagnose system problems, when the diagnostic terminal is grounded
with a spare fuse in the fuse box.
As a bulb and system check, the light will come "ON" with the key "ON" and the engine not running. When the engine is started, the light will turn
"OFF." If the light remains "ON," the self-diagnostic system has detected a problem. If the problem goes away, the light will go out in most cases after
10 seconds, but a Trouble Code will remain stored in the ECM. When the light remains "ON" while the engine is running, or when a malfunction is
suspected due to a driveability or emissions problem, a DIAGNOSTIC CIRCUIT CHECK must be performed.
The ECM and "CHECK ENGINE" light operates as follows:
The "CHECK ENGINE" light illuminates when the ignition switch is turned "ON" (but the engine is stopped) with the diagnosis switch terminal
ungrounded regardless of the condition of EFI system. This is only to check the "CHECK ENGINE" light bulb and its circuit. If the EFI system is free
from any faults after the engine starts (while engine is running), the "CHECK ENGINE" light turns "OFF." If any trouble exists, it may turn "OFF" but
only until the ECM detects that fault. When ECM detects a trouble which has occurred in the above areas, it turns the "CHECK ENGINE" light "ON"
while the engine is running to warn the driver of the occurrence of a fault and at the same time it stores the trouble code in ECM back-up memory. (The
code is kept in memory even if the fault was only temporary and disappeared immediately. It is not erased unless the power to ECM is shut off for 20
seconds or longer.) The ECM also indicates trouble codes in memory by means of flashing of "CHECK ENGINE" light at the time of inspection (i.e.
when the diagnosis switch terminal is grounded and ignition switch is turned "ON").
Even when trouble has occurred in the EFI system and a fault is detected by the ECM, control over the injector, ISC solenoid valve and others is
maintained on the basis of the standard signals and/or back-up program prestored in the ECM. This function is called "fail-safe function." Thus, with this
function, a certain level of engine performance is available even when some failure occurs and disability in running is avoided. The systems covered are
as follows:
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Coolant Temperature Sensor.
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Throttle Switch (M/T model) or Throttle Position Sensor (A/T model).
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Vehicle Speed Sensor.
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Manifold Air Temperature Sensor.
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Manifold Absolute Pressure Sensor.
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CPU in the ECM.
