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1F – 410 ENGINE CONTROLS
GENERAL DESCRIPTION
AND SYSTEM OPERATION
IGNITION SYSTEM OPERATION
This ignition system does not use a conventional distrib-
utor and coil. It uses a crankshaft position sensor input
to the engine control
module (ECM). The ECM then determines Elec-
tronic Spark Timing (EST) and triggers the electronic
ignition system ignition coil.
This type of distributorless ignition system uses a "waste
spark" method of spark distribution. Each cylinder is
paired with the cylinder that is opposite it (1-4 or 2-3).
The spark occurs simultaneously in the cylinder coming
up on the compression stroke and in the cylinder coming
up on the exhaust stroke. The cylinder on the exhaust
stroke requires very little of the available energy to fire
the spark plug. The remaining energy is available to the
spark plug in the cylinder on the compression stroke.
These systems use the EST signal from the ECM
to control the electronic spark timing. The ECM
uses the following information:
D Engine load (manifold pressure or vacuum).
D Atmospheric (barometric) pressure.
D Engine temperature.
D Intake air temperature.
D Crankshaft position.
D Engine speed (rpm).
ELECTRONIC IGNITION SYSTEM
IGNITION COIL
The Electronic Ignition (EI) system ignition coil is
mounted near the rear of the camshaft carrier on the
single overhead camshaft engine. On the dual overhead
camshaft engine, the EI system ignition coil is mounted
near the rear of the cylinder head. Each pair of terminals
of the EI system ignition coil provides the spark for two
spark plugs simultaneously. The EI system ignition coil
is not serviceable and must be replaced as an assembly.
CRANKSHAFT POSITION SENSOR
This electronic ignition system uses a magnetic crank-
shaft position sensor mounted just ahead of the block
below the intake manifold. This sensor protrudes
through its mount to within approximately 1.3 mm (0.05
inch) of the crankshaft reluctor. The reluctor is a special
wheel attached to the crankshaft pulley with 58 slots ma-
chines into it, 57 of which are equally spaced in 6 degree
intervals. The last slot is wider and serves to generate a
"sync pulse." As the crankshaft rotates, the slots in the
reluctor change the magnetic field of the sensor, creat-
ing an induced voltage pulse. The longer pulse of the
58th slot identifies a specific orientation of the crank-
shaft and allows the
engine control module (ECM) to determine the
crankshaft orientation at all times. The ECM uses
this information to generate timed ignition and injection
pulses that it sends to the ignition coils and to the fuel
injectors.
CAMSHAFT POSITION SENSOR
The Camshaft Position (CMP) sensor sends a CMP
sensor signal to the
engine control module (ECM). The ECM
uses this signal as a "sync pulse" to trigger the injectors
in the proper sequence. The ECM uses the CMP
sensor signal to indicate the position of the #1 piston
during its power stroke. This allows the ECM to
calculate true sequential fuel injection mode of opera-
tion. If the ECM detects an incorrect CMP sensor
signal while the engine is running, DTC P0341 will set. If
the CMP sensor signal is lost while the engine is run-
ning, the fuel injection system will shift to a calculated
sequential fuel injection mode based on the last fuel in-
jection pulse, and the engine will continue to run. As long
as the fault is present, the engine can be restarted. It will
run in the calculated sequential mode with a
1-in-6 chance of the injector sequence being correct.
IDLE AIR SYSTEM OPERATION
The idle air system operation is controlled by the base
idle setting of the throttle body and the Idle Air Control
(IAC) valve.
The engine control
module (ECM) uses the IAC valve to set the idle speed
dependent on conditions. The ECM uses informa-
tion from various inputs, such as coolant temperature,
manifold vacuum, etc., for the effective control of the idle
speed.
FUEL CONTROL SYSTEM
OPERATION
The function of the fuel metering system is to deliver the
correct amount of fuel to the engine under all operating
conditions. The fuel is delivered to the engine by the in-
dividual fuel injectors mounted into the intake manifold
near each cylinder.
The two main fuel control sensors are the Manifold Ab-
solute Pressure (MAP) sensor and the Oxygen (O2S 1)
Sensor.
The MAP sensor measures or senses the intake man-
ifold vacuum. Under high fuel demands the MAP sensor
reads a low vacuum condition, such as wide open
throttle. The engine
control module (ECM) uses this information to richen the
mixture, thus increasing the fuel injector on-time, to pro-
vide the correct amount of fuel. When decelerating, the
vacuum increases. This vacuum change is sensed by
DAEWOO T-154 BL2,3
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