MIL Operation
The PCM controlled lamps are intended to alert the driver to an operating
condition which may require immediate attention. Ignition positive voltage
powers the PCM controlled lamps. The PCM commands the lamps ON by applying
ground to the lamp control circuit.
The Malfunction Indicator Lamp (MIL) is located on the instrument panel
(CHECK ENGINE) or (SERVICE ENGINE SOON). The MIL performs the following functions:
| • | It informs the driver that a problem has occurred and that the
vehicle should be taken for service as soon as possible. |
| • | As a bulb check and system check, the MIL will illuminate with
the ignition switch ON and the engine not running. when the engine is started,
the MIL will turn OFF. If the MIL remains ON, the self-diagnostic system
has detected a problem. If the problem goes away, the MIL will turn OFF
in most cases, but a diagnostic trouble code will remain stored. |
| • | If the MIL is illuminated, then the engine stalls, the MIL will
remain Illuminated so long as the ignition switch is ON. |
| • | Now, if the MIL is not illuminated and the engine stalls, the
MIL will not illuminate until the ignition switch is cycled OFF, then ON. |
Perform the Powertrain On-Board Diagnostic System Check first, when
the following conditions are present:
| • | When the MIL does not turn ON when the the ignition switch is
turned to the RUN position |
| • | When the MIL remains ON while the engine is running |
| • | When you suspect a driveability problem |
| • | When you suspect an emissions problem |
Low Oil Level Lamp
The PCM commands the Low Oil Level Lamp ON if the engine oil level switch
indicates that a low oil level condition exists. The PCM determines whether
or not to test for low oil level based on the difference between engine
coolant temperature at the last shutdown and engine coolant temperature
at startup. This is to ensure that the oil has drained back into the
oil pan before testing.
The engine oil level switch is a simple float switch that is grounded
when the engine oil level is OK. When the ignition is first turned ON, the
PCM commands the Low Oil Level lamp ON for a brief period of time to
test the bulb (approximately 3 seconds). The PCM also checks the engine
oil level switch circuit at startup. If the engine has been running,
the PCM performs a test routine based on engine coolant temperature to
ensure that the engine oil drained back into the sump before checking
the state of the engine oil level switch. If the engine coolant temperature
is between 15°C (59°F) and 130°C (266°F), the PCM compares
the engine coolant temperature at the last key OFF to the engine coolant
temperature at the current key ON. If the difference between the recorded
temperature values is at least 12°C(54°F), the PCM will test the
engine oil level.
Generator Lamp
The PCM commands the generator lamp ON under the following conditions:
| • | When the engine speed is greater than 1200 rpm and system
voltage falls below 10 volts for longer than 10 seconds. The
PCM commands the generator lamp OFF when system voltage rises to above
12 volts. |
| • | When the generator control circuit (L terminal) remains low for
longer than 10 seconds. |
Change Oil Lamp
The PCM commands the Oil Life Monitor lamp ON when an oil change is
required. The PCM calculates remaing oil life based on total engine revolutions
and calculated engine oil temperature for each startup since the Oil
Life monitor was reset.
