6E1–307
X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Engine Control Module (ECM)
The engine control module (ECM) is located in the
passenger compartment below the center console. The
ECM controls the following:
D
Fuel metering system.
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Ignition timing.
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On–board diagnostics for powertrain functions.
The ECM constantly observes the information from
various sensors. The ECM controls the systems that
affect vehicle performance. The ECM performs the
diagnostic function of the system. It can recognize
operational problems, alert the driver through the Check
Engine lamp, and store diagnostic trouble codes (DTCs).
DTCs identify the problem areas to aid the technician in
making repairs.
014RX002
ECM Function
The ECM supplies either 5 or 12 volts to power various
sensors or switches. The power is supplied through
resistors in the ECM which are so high in value that a test
light will not light when connected to the circuit. In some
cases, even an ordinary shop voltmeter will not give an
accurate reading because its resistance is too low.
Therefore, a digital voltmeter with at least 10 meg
W
input
impedance is required to ensure accurate voltage
readings. Tool J 39200 meets this requirement.
The ECM controls output circuits such as the injectors,
IAC, cooling fan relays, etc., by controlling the ground or
the power feed circuit through transistors or through
either of the following two devices:
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Output Driver Module (ODM)
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Quad Driver Module (QDM)
ECM Components
The ECM is designed to maintain exhaust emission levels
to government mandated standards while providing
excellent driveability and fuel efficiency. The ECM
monitors numerous engine and vehicle functions via
electronic sensors such as the throttle position (TP)
sensor, heated oxygen sensor (HO2S), and vehicle
speed sensor (VSS). The ECM also controls certain
engine operations through the following:
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Fuel injector control
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Ignition control module
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Evaporative emission (EVAP) purge
D
A/C clutch control
ECM Voltage Description
The ECM supplies a buffered voltage to various switches
and sensors. It can do this because resistors in the ECM
which are so high in value that a test light may not
illuminate when connected to the circuit. An ordinary shop
voltmeter may not give an accurate reading because the
voltmeter input impedance is too low. Use a 10–megohm
input impedance digital voltmeter (such as J 39200) to
assure accurate voltage readings.
The input/output devices in the ECM include
analog–to–digital converters, signal buffers, counters,
and special drivers. The ECM controls most components
with electronic switches which complete a ground circuit
when turned ON. These switches are arranged in groups
of 4 and 7, called either a quad driver module (QDM),
which can independently control up to 4 output terminals,
or Output Driver Module (ODM) which can independently
control up to 7 outputs. Not all outputs are always used.
ECM Inputs/Outputs
Inputs – Operating Conditions Read
D
Air Conditioning Compressor Clutch ON or OFF
D
Engine Coolant Temperature
D
Crankshaft Position
D
Exhaust Oxygen Content
D
Manifold Absolute Pressure
D
Battery Voltage
D
Throttle Position
D
Fuel Tank Vapor Pressure
D
Fuel Tank Level
D
Exhaust Gas Recirculation (EGR) Feedback
D
Knock
D
Vehicle Speed
D
Fuel Pump Voltage
D
Power Steering Pressure
D
Intake Air Temperature
D
Camshaft Position
Outputs – Systems Controlled
D
EVAP Canister Purge Solenoid
D
Exhaust Gas Recirculation (EGR)
D
Ignition Control
D
Fuel Injector Control
D
Idle Air Control
D
Coolant Fan Relays
D
Electric Fuel Pump Relay Compressor Clutch Relay
D
Air Conditioning