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Volts
4.9
4.4
kPa
0
10
in Hg
0
2.9
ENGINE CONTROL MODULE
The engine control
module
(ECM), located in passenger comportment, is the
control center of the fuel injection system. It constantly
looks at the information from various sensors and con-
trols the systems that affect the vehicle's performance.
The
ECM also performs the diagnostic functions of
the system. It can recognize operational problems, alert
the driver through the Service Reminder Indicator (SRI),
and store diagnostic trouble code(s) which identify the
problem areas to aid the technician in making repairs.
There are no serviceable parts in the ECM. The
calibrations are stored in the ECM in the Program-
mable Read Only Memory (PROM).
The ECM supplies either 5 or 12 volts to power the
sensors or switches. This is done through resistances in
the ECM which are so high in value that a test light
will not come on 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. You
must use a digital voltmeter with a 10 megohm input im-
pedance to get accurate voltage readings. The
ECM controls output circuits such as the fuel injectors,
the Idle Air Control (IAC) valve, the A/C clutch relay,
etc., by controlling the ground circuit through transistors
or a device called a "quad-driver."
FUEL INJECTOR
The Multi-Port Fuel Injection (MPFI) assembly is a sole-
noid-operated device controlled by the powertrain con-
trol module engine control module (ECM) that
meters pressurized fuel to a single engine cylinder. The
ECM energizes the fuel injector or solenoid to a
normally closed ball or pintle valve. This allows fuel to
flow into the top of the injector, past the ball or pintle
valve, and through a recessed flow director plate at the
injector outlet.
The director plate has six machined holes that control
the fuel flow, generating a conical spray pattern of finely
atomized fuel at the injector tip. Fuel from the tip is di-
rected at the intake valve, causing it to become further
atomized and vaporized before entering the combustion
chamber. A fuel injector which is stuck partially open
would cause a loss of fuel pressure after the engine is
shut down. Also, an extended crank time would be no-
ticed on some engines. Dieseling could also occur be-
DAEWOO T-154 BL2,3
VACUUM
3.8
3.3
2.7
20
30
40
5.9
8.9
11.8
ENGINE CONTROLS 1F – 415
2.2
1.7
1.1
50
60
70
14.8
17.7
20.7
cause some fuel could be delivered to the engine after
the ignition is turned OFF.
STRATEGY-BASED DIAGNOSTICS
Strategy-Based Diagnostics
The strategy-based diagnostic is a uniform approach to
repair all Electrical/Electronic (E/E) systems. The diag-
nostic flow can always be used to resolve an E/E system
problem and is a starting point when repairs are neces-
sary. The following steps will instruct the technician on
how to proceed with a diagnosis:
D Verify the customer complaint. To verify the customer
complaint, the technician should know the normal op-
eration of the system.
D Perform preliminary checks as follows:
D Conduct a thorough visual inspection.
D Review the service history.
D Detect unusual sounds or odors.
D Gather diagnostic trouble code information to
achieve an effective repair.
D Check bulletins and other service information. This
includes videos, newsletters, etc.
D Refer to service information (manual) system
check(s).
D Refer to service diagnostics.
No Trouble Found
This condition exists when the vehicle is found to oper-
ate normally. The condition described by the customer
may be normal. Verify the customer complaint against
another vehicle that is operating normally. The condition
may be intermittent. Verify the complaint under the con-
ditions described by the customer before releasing the
vehicle.
Re-examine the complaint.
When the complaint cannot be successfully found or iso-
lated, a re-evaluation is necessary. The complaint
should be re-verified and could be intermittent as de-
fined in "Intermittents", or could be normal.
After isolating the cause, the repairs should be made.
Validate for proper operation and verify that the symp-
tom has been corrected. This may involve road testing
or other methods to verify that the complaint has been
resolved under the following conditions:
D Conditions noted by the customer.
0.6
0.3
0.3
80
90
100
23.7
26.7
29.6
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