Daewoo NUBIRA, User Manual

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1F – 408 I ENGINE CONTROLS
DAEWOO V–121 BL4
MANIFOLD ABSOLUTE PRESSURE
SENSOR
The Manifold Absolute Pressure (MAP) sensor measures
the changes in the intake manifold pressure which result
from engine load and speed changes. It converts these to
a voltage output.
A closed throttle on engine coast down produces a rela-
tively low MAP output. MAP is the opposite of vacuum.
When manifold pressure is high, vacuum is low. The MAP
sensor is also used to measure barometric pressure. This
is performed as part of MAP sensor calculations. With the
ignition ON and the engine not running, the powertrain
control module (PCM)/engine control module (ECM) will
read the manifold pressure as barometric pressure and
adjust the air/fuel ratio accordingly. This compensation for
altitude allows the system to maintain driving performance
while holding emissions low. The barometric function will
update periodically during steady driving or under a wide
open throttle condition. In the case of a fault in the baro-
metric portion of the MAP sensor, the PCM/ECM will set
to the default value.
A failure in the MAP sensor circuit sets a diagnostic trouble
code P0107 or P0108.
The following tables show the difference between absolute pressure and vacuum related to MAP sensor output, which
appears as the top row of both tables.
MAP
Volts 4.9 4.4 3.8 3.3 2.7 2.2 1.7 1.1 0.6 0.3 0.3
kPa 100 90 80 70 60 50 40 30 20 10 0
in. Hg 29.6 26.6 23.7 20.7 17.7 14.8 11.8 8.9 5.9 2.9 0
VACUUM
Volts 4.9 4.4 3.8 3.3 2.7 2.2 1.7 1.1 0.6 0.3 0.3
kPa 0 10 20 30 40 50 60 70 80 90 100
in. Hg 0 2.9 5.9 8.9 11.8 14.8 17..7 20.7 23.7 26.7 29.6
POWERTRAIN CONTROL
MODULE/ENGINE CONTROL
MODULE
The powertrain control module (PCM)/engine control
module (ECM), located inside the passenger kick–panel,
is the control center of the fuel injection system. It
constantly looks at the information from various sensors
and controls the systems that affect the vehicle’s perfor-
mance. The PCM/ECM also performs the diagnostic func-
tions of the system. It can recognize operational problems,
alert the driver through the Malfunction Indicator Lamp
(MIL), and store diagnostic trouble code(s) which identify
problem areas to aid the technician in making repairs.
There are no serviceable parts in the PCM/ECM. The cal-
ibrations are stored in the PCM/ECM in the Programmable
Read–Only Memory (PROM).
The PCM/ECM supplies either 5 or 12 volts to power the
sensors or switches. This is done through resistances in
the PCM/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 ac-
curate reading because its resistance is too low. You must
use a digital voltmeter with a 10 megohm input impedance
to get accurate voltage readings. The PCM/ECM controls
output circuits such as the fuel injectors, the idle air control
valve, the A/C clutch relay, etc., by controlling the ground
circuit through transistors or a device called a ”quad–driv-
er.”
FUEL INJECTOR
The Multiport Fuel Injection (MFI) assembly is a solenoid–
operated device controlled by the powertrain control mod-
ule (PCM)/engine control module (ECM). It meters pres-
surized fuel to a single engine cylinder. The PCM/ECM
energizes the fuel injector or the 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 atom-
ized fuel at the injector tip. Fuel from the tip is directed 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 will cause a loss
of fuel pressure after the engine is shut down. Also, an ex-
tended crank time will be noticed on some engines. Diesel-
ing can also occur because some fuel can be delivered to
the engine after the ignition is turned OFF.
KNOCK SENSOR
The knock sensor detects abnormal knocking in the en-
gine. The sensor is mounted in the engine block near the
cylinders. The sensor produces an AC output voltage
which increases with the severity of the knock. This signal