width NISSAN LATIO 2009 Service User Guide
[x] Cancel search | Manufacturer: NISSAN, Model Year: 2009, Model line: LATIO, Model: NISSAN LATIO 2009Pages: 4331, PDF Size: 58.04 MB
Page 1235 of 4331

CVT
N
O P
DTC P0841 PRESSURE SENSOR FUNCTION
Description INFOID:0000000004305717
Using the engine load (throttle position), the primary pulley revolution speed, and the secondary pulley revolu-
tion speed as input signal, TCM changes the operating pr essure of the primary pulley and the secondary pul-
ley and changes the groove width of the pulley to control the gear ratio.
CONSULT-III Reference Val ue in Data Monitor Mode INFOID:0000000004305718
Remarks: Specification data are reference values.
On Board Diagnosis Logic INFOID:0000000004305719
• This is not an OBD-II self-diagnostic item.
• Diagnostic trouble code “P0841 PRESS SEN/FNCTN” with CONSULT-III is detected when secondary fluid
pressure is too high compared with the commanded value while driving.
Possible Cause INFOID:0000000004305720
• Transmission fluid pressure sensor A (Secondary pressure sensor)
• Harness or connectors
(Sensor circuit is open or shorted.)
DTC Confirmation Procedure INFOID:0000000004305721
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If “DTC Confirmation Procedure” has been previously performed, alw ays turn ignition switch OFF and
wait at least 10 seconds before performing the next test.
After the repair, perform the following procedure to confirm the malfunction is eliminated.
WITH CONSULT-III
1. Turn ignition switch ON and select “DATA MO NITOR” mode for “TRANSMISSION” with CONSULT-III.
2. Start engine and maintain the following conditions for at least 12 consecutive seconds. VEHICLE SPEED: 40 km/h (25 MPH) More than
RANGE: “D” position
3. If DTC is detected, go to CVT-291, " Diagnosis Procedure " .
Diagnosis Procedure INFOID:0000000004305722CONSULT-III Function (TRANSMISSION) " .
Is any malfunction of the “ U1000 CAN COMM CIRCUIT ” indicated?
YES >> Check CAN communication line. Refer to
CVT-238 .
NO >> GO TO 2.
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*3: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of
time the valve remains open (injection pulse duration). T he amount of fuel injected is a program value in the
ECM memory. The program value is preset by engi ne operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from t he crankshaft position sensor (POS), camshaft position
sensor (PHASE) and the mass air flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION In addition, the amount of fuel injected is compens ated to improve engine performance under various operat-
ing conditions as listed below.
• During warm-up
• When starting the engine
• During acceleration
• Hot-engine operation
• When selector lever is changed from N to D (A/T models)
• High-load, high-speed operation
• During deceleration
• During high engine speed operation
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system prov ides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst (manifold) can better reduce CO, HC and NOx emissions. This system uses A/F sen-
sor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM adjusts the
injection pulse width according to the sensor voltage si gnal. For more information about A/F sensor 1, refer to
EC-182, " Description " . This maintains the mixture ratio within t
he range of stoichiometric (ideal air-fuel mix-
ture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the th ree way catalyst (manifold). Even if the switching
characteristics of A/F sensor 1 shift, the air-fuel rati o is controlled to stoichiometric by the signal from heated
oxygen sensor 2.
• Open Loop Control
The open loop system condition refers to when the EC M detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
- Deceleration and acceleration
- High-load, high-speed operation
- Malfunction of A/F sensor 1 or its circuit
- Insufficient activation of A/F sensor 1 at low engine coolant temperature
- High engine coolant temperature
- During warm-up
- After shifting from N to D (A/T models)
- When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL The mixture ratio feedback control system monitors the mixture ratio signal transmitted from A/F sensor 1.
This feedback signal is then sent to the ECM. The ECM cont rols the basic mixture ratio as close to the theoret-
ical mixture ratio as possible. However, the basic mi xture ratio is not necessarily controlled as originally
Page 1407 of 4331

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ELECTRIC IGNITION SYSTEM
System Diagram INFOID:0000000004780014
System Description INFOID:0000000004780015
INPUT/OUTPUT SIGNAL CHART
*1: This signal is sent to the ECM via the CAN communication line.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION Ignition order: 1 - 3 - 4 - 2
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of the
engine. The ignition timing data is stored in the ECM.
The ECM receives information such as the injecti on pulse width and camshaft position sensor (PHASE) sig-
nal. Computing this information, ignition si gnals are transmitted to the power transistor.
During the following conditions, the ignition timing is revi sed by the ECM according to the other data stored in
the ECM.
• At starting
• During warm-up
• At idle
• At low battery voltage
• During acceleration
Page 1462 of 4331

Monitored item Unit Description Remarks
ENG SPEED rpm • Indicates the engine speed computed from the signal
of the crankshaft position sensor (POS) and camshaft
position sensor (PHASE). • Accuracy becomes poor if engine
speed drops below the idle rpm.
• If the signal is interrupted while the engine is running, an abnormal value
may be indicated.
MAS A/F SE-B1 V • The signal voltage of the mass air flow sensor is dis-
played. • When the engine is stopped, a certain
value is indicated.
• When engine is running specification range is indicated in “SPEC”.
B/FUEL SCHDL ms • “Base fuel schedule” indicates the fuel injection pulse
width programmed into ECM, prior to any learned on
board correction. • When engine is running specification
range is indicated in “SPEC”.
A/F ALPHA-B1 % • The mean value of the air-fuel ratio feedback correc-
tion factor per cycle is indicated. • When the engine is stopped, a certain
value is indicated.
• This data also includes the data for
the air-fuel ratio learning control.
• When engine is running specification range is indicated in “SPEC”.
COOLAN TEMP/S °C or °F • The engine coolant temperature (determined by the
signal voltage of the engine coolant temperature sen-
sor) is displayed. • When the engine coolant temperature
sensor is open or short-circuited,
ECM enters fail-safe mode. The en-
gine coolant temperature determined
by the ECM is displayed.
A/F SEN1 (B1) V • The A/F signal computed from the input signal of the
air fuel ratio (A/F) se nsor 1 is displayed.
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HO2S2 (B1) V
• The signal voltage of the heated oxygen sensor 2 is
displayed.
HO2S2 MNTR(B1) RICH/
LEAN • Display of heated oxygen sensor 2 signal:
RICH: means the amount of oxygen after three way
catalyst is relatively small.
LEAN: means the amount of oxygen after three way
catalyst is relatively large. • When the engine is stopped, a certain
value is indicated.
VHCL SPEED SE km/h or
mph • The vehicle speed computed from the vehicle speed
signal sent from combination meter is displayed.
BATTERY VOLT V • The power supply voltage of ECM is displayed.
ACCEL SEN 1 V• The accelerator pedal position sensor signal voltage is
displayed. • ACCEL SEN 2 signal is converted by
ECM internally. Thus, it differs from
ECM terminal voltage signal.
ACCEL SEN 2
TP SEN 1-B1 V• The throttle position sensor signal voltage is dis-
played. • TP SEN 2-B1 signal is converted by
ECM internally. Thus, it differs from
ECM terminal voltage signal.
TP SEN 2-B1
FUEL T/TMP SE °C or °F • The fuel temperature (determined by the signal volt-
age of the fuel tank temperature sensor) is displayed.
INT/A TEMP SE °C or °F • The intake air temperature (determined by the signal
voltage of the intake air temperature sensor) is indicat-
ed.
EVAP SYS PRES V • The signal voltage of EVAP control system pressure
sensor is displayed.
FUEL LEVEL SE V • The signal voltage of the fuel level sensor is displayed.
START SIGNAL ON/OFF • Indicates start signal status [ON/OFF] computed by
the ECM according to the signals of engine speed and
battery voltage. • After starting the engine, [OFF] is dis-
played regardless of the starter sig-
nal.
CLSD THL POS ON/OFF • Indicates idle position [ON/OFF] computed by ECM
according to the accelerator pedal position sensor sig-
nal.
AIR COND SIG ON/OFF • Indicates [ON/OFF] condition of the air conditioner
switch determined by the air conditioner ON signal.
P/N POSI SW ON/OFF • Indicates [ON/OFF] condit
ion from the park/neutral
position (PNP) switch signal.
PW/ST SIGNAL ON/OFF • [ON/OFF] condition of the power steering system (de-
termined by the signal sent from EPS control unit) is
indicated.
LOAD SIGNAL ON/OFF • Indicates [ON/OFF] condition from the electrical load
signal.
ON: Rear window defogger switch is ON and/or light-
ing switch is in 2nd position.
OFF: Both rear window defogger switch and lighting
switch are OFF.
IGNITION SW ON/OFF • Indicates [ON/OFF] condition from ignition switch sig-
nal.
HEATER FAN SW ON/OFF • Indicates [ON/OFF] condition from the heater fan
switch signal.
BRAKE SW ON/OFF • Indicates [ON/OFF] condition from the stop lamp
switch signal.
INJ PULSE-B1 msec • Indicates the actual fuel injection pulse width compen-
sated by ECM according to the input signals. • When the engine is stopped, a certain
computed value is indicated.
IGN TIMING BTDC • Indicates the ignition timing computed by ECM ac-
cording to the input signals. • When the engine is stopped, a certain
value is indicated.
CAL/LD VALUE % • “Calculated load value” indicates the value of the cur-
rent air flow divided by peak air flow.
Monitored item Unit Description Remarks
Page 1876 of 4331
![NISSAN LATIO 2009 Service User Guide EC-520< SERVICE INFOMATION >
[MR TYPE 1]
ENGINE CONTROL SYSTEM
The mixture ratio feedback system provides the best air/ fuel mixture ratio for driveability and emission control.
The three way catal NISSAN LATIO 2009 Service User Guide EC-520< SERVICE INFOMATION >
[MR TYPE 1]
ENGINE CONTROL SYSTEM
The mixture ratio feedback system provides the best air/ fuel mixture ratio for driveability and emission control.
The three way catal](/img/5/57359/w960_57359-1875.png)
EC-520< SERVICE INFOMATION >
[MR TYPE 1]
ENGINE CONTROL SYSTEM
The mixture ratio feedback system provides the best air/ fuel mixture ratio for driveability and emission control.
The three way catalyst (manifold) can then better r educe CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The
ECM adjusts the injection pulse width according to t he sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to EC-698 . This maintains the mixture ratio within the range of stoichiometric
(ideal air/fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the th ree way catalyst (manifold). Even if the switching
characteristics of air fuel ratio (A/F) sensor 1 shift, the air/fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Open Loop Control
The open loop system condition refers to when the EC M detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
• Deceleration and acceleration
• High-load, high-speed operation
• Malfunction of air fuel ratio (A/F) sensor 1 or its circuit
• Insufficient activation of air fuel ratio (A /F) sensor 1 at low engine coolant temperature
• High engine coolant temperature
• During warm-up
• After shifting from N to D (A/T and CVT models)
• When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixt ure ratio signal transmitted from air fuel ratio (A/F)
sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to
the theoretical mixture ratio as possible. However, the bas ic mixture ratio is not necessarily controlled as orig-
inally designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic
changes during operation (i.e., fuel injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is
then computed in terms of “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value co mpared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensati on used to maintain the mixture ratio at its theoretical
value. The signal from air fuel ratio (A/F) sensor 1 i ndicates whether the mixture ratio is RICH or LEAN com-
pared to the theoretical value. The signal then triggers a r eduction in fuel volume if the mixture ratio is rich, and
an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation carri ed out long-term to compensate for continual deviation
of the short term fuel trim from t he central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder during each engine cycl e according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System
Fuel is injected simultaneously into all four cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The four fuel injectors will then receive the signals two times for each engine cycle. SEF337W
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This system is used when the engine is being started
and/or if the fail-safe system (CPU) is operating.
FUEL SHUT-OFF Fuel to each cylinder is cut off during deceleration, operation of the engine at excessively high speeds or oper-
ation of the vehicle at excessively high speeds.
Electronic Ignition (EI) System INFOID:0000000004537021
INPUT/OUTPUT SIGNAL CHART
*1: This signal is sent to the ECM through CAN communication line.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION Firing order: 1 - 3 - 4 - 2
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of the
engine. The ignition timing data is stored in the ECM.
The ECM receives information such as the injecti on pulse width and camshaft position sensor (PHASE) sig-
nal. Computing this information, ignition si gnals are transmitted to the power transistor.
During the following conditions, the ignition timing is revi sed by the ECM according to the other data stored in
the ECM.
• At starting
• During warm-up
• At idle
• At low battery voltage
• During acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.
Fuel Cut Control (at No Load and High Engine Speed) INFOID:0000000004537022
INPUT/OUTPUT SIGNAL CHART Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS) Engine speed*2
Piston position
Ignition timing
control Power transistor
Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Battery Battery voltage*2
Knock sensor Engine knocking
Park/neutral position (PNP) switch Gear position
ABS actuator and electric unit (control unit) Vehicle speed*1
Combination meter Sensor Input Signal to ECM ECM function Actuator
Park/neutral position (PNP) switch Neutral position
Fuel cut control Fuel injector
Accelerator pedal position sensor Accelerator pedal position
Engine coolant temperature sensor Engine coolant temperature
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed
ABS actuator and electric unit (control unit) Vehicle speed*
Combination meter
Page 1964 of 4331
![NISSAN LATIO 2009 Service User Guide Monitored item [Unit] Description Remarks
ENG SPEED
[rpm] • Indicates the engine speed computed from the signals of the
crankshaft position sensor (POS) and camshaft position sen-
sor (PHASE). • NISSAN LATIO 2009 Service User Guide Monitored item [Unit] Description Remarks
ENG SPEED
[rpm] • Indicates the engine speed computed from the signals of the
crankshaft position sensor (POS) and camshaft position sen-
sor (PHASE). •](/img/5/57359/w960_57359-1963.png)
Monitored item [Unit] Description Remarks
ENG SPEED
[rpm] • Indicates the engine speed computed from the signals of the
crankshaft position sensor (POS) and camshaft position sen-
sor (PHASE). • Accuracy becomes poor if engine speed
drops below the idle rpm.
• If the signal is interrupted while the engine is running, an abnormal value may be indicat-
ed.
MAS A/F SE-B1
[V] • The signal voltage of the mass air flow sensor is displayed. • When the engine is stopped, a certain value
is indicated.
• When engine is running, specification range is indicated in "SPEC".
B/FUEL SCHDL
[msec] • “Base fuel schedule” indicates the fuel injection pulse width
programmed into ECM, prior to any learned on board correc-
tion. • When engine is running, specification range
is indicated in "SPEC".
A/F ALPHA-B1
[%] • The mean value of the air-fuel ratio feedback correction fac-
tor per cycle is indicated. • When the engine is stopped, a certain value
is indicated.
• This data also includes the data for the air/ fuel ratio learning control.
• When engine is running, specification range
is indicated in "SPEC".
COOLAN TEMP/S
[ ° C] or [ °F] • The engine coolant temperature (determined by the signal
voltage of the engine coolant temperature sensor) is dis-
played. • When the engine coolant temperature sen-
sor is open or short-circuited, ECM enters
fail-safe mode. The engine coolant temper-
ature determined by the ECM is displayed.
A/F SEN1 (B1)
[V] • The A/F signal computed from the input signal of the A/F sen-
sor 1 is displayed.
HO2S2 (B1)
[V] • The signal voltage of the heated oxygen sensor 2 is dis-
played.
HO2S2 MNTR (B1)
[RICH/LEAN] • Display of heated oxygen sensor 2 signal:
RICH: means the amount of oxygen after three way catalyst
is relatively small.
LEAN: means the amount of oxygen after three way catalyst
is relatively large. • When the engine is stopped, a certain value
is indicated.
VHCL SPEED SE
[km/h] or [mph] • The vehicle speed computed from the vehicle speed signal is
displayed.
BATTERY VOLT
[V] • The power supply voltage of ECM is displayed.
ACCEL SEN 1
[V] • The accelerator pedal position sensor signal voltage is dis-
played. • ACCEL SEN 2 signal is converted by ECM
internally. Thus, it differs from ECM terminal
voltage signal.
ACCEL SEN 2
[V]
TP SEN 1-B1
[V] • The throttle position sensor signal voltage is displayed. • TP SEN 2-B1 signal is converted by ECM in-
ternally. Thus, it differs from ECM terminal
voltage signal.
TP SEN 2-B1
[V]
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![NISSAN LATIO 2009 Service User Guide EC
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FUEL T/TMP SE
[ ° C] or [ °F] • The fuel temperature (determined by the signal voltage of the
fuel tank temperature sensor) is displayed.
INT/A TEMP SE
[ ° C] or [ °F] • The intake ai NISSAN LATIO 2009 Service User Guide EC
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FUEL T/TMP SE
[ ° C] or [ °F] • The fuel temperature (determined by the signal voltage of the
fuel tank temperature sensor) is displayed.
INT/A TEMP SE
[ ° C] or [ °F] • The intake ai](/img/5/57359/w960_57359-1964.png)
EC
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FUEL T/TMP SE
[ ° C] or [ °F] • The fuel temperature (determined by the signal voltage of the
fuel tank temperature sensor) is displayed.
INT/A TEMP SE
[ ° C] or [ °F] • The intake air temperature (determined by the signal voltage
of the intake air temperature sensor) is indicated.
EVAP SYS PRES
[V] • The signal voltage of EVAP control system pressure sensor
is displayed.
FUEL LEVEL SE
[V] • The signal voltage of the fuel level sensor is displayed.
START SIGNAL
[ON/OFF] • Indicates start signal status [ON/OFF] computed by the ECM
according to the signals of engine speed and battery voltage. • After starting the engine, [OFF] is displayed
regardless of the starter signal.
CLSD THL POS
[ON/OFF] • Indicates idle position [ON/OFF] computed by the ECM ac-
cording to the accelerator pedal position sensor signal.
AIR COND SIG
[ON/OFF] • Indicates [ON/OFF] condition of the air conditioner switch as
determined by the air conditioner signal.
P/N POSI SW
[ON/OFF] • Indicates [ON/OFF] condition from the park/neutral position
(PNP) switch signal.
PW/ST SIGNAL
[ON/OFF] • [ON/OFF] condition of the power steering system (deter-
mined by the signal sent from EPS control unit) is indicated.
LOAD SIGNAL
[ON/OFF] • Indicates [ON/OFF] condition from the electrical load signal.
ON: Rear window defogger switch is ON and/or lighting
switch is in 2nd position.
OFF: Both rear window defogger switch and lighting switch
are OFF.
IGNITION SW
[ON/OFF] • Indicates [ON/OFF] condition from ignition switch.
HEATER FAN SW
[ON/OFF] • Indicates [ON/OFF] condition from the heater fan switch sig-
nal.
BRAKE SW
[ON/OFF] • Indicates [ON/OFF] condition from the stop lamp switch sig-
nal.
INJ PULSE-B1
[msec] • Indicates the actual fuel injection pulse width compensated
by ECM according to the input signals. • When the engine is stopped, a certain com-
puted value is indicated.
IGN TIMING
[BTDC] • Indicates the ignition timing computed by ECM according to
the input signals. • When the engine is stopped, a certain value
is indicated.
CAL/LD VALUE
[%] • “Calculated load value” indicates the value of the current air-
flow divided by peak airflow.
MASS AIRFLOW
[g·m/s] • Indicates the mass airflow computed by ECM according to
the signal voltage of the mass air flow sensor.
PURG VOL C/V
[%] • Indicates the EVAP canister purge volume control solenoid
valve control value computed by the ECM according to the in-
put signals.
• The opening becomes larger as the value increases.
INT/V TIM (B1)
[ ° CA] • Indicates [
°CA] of intake camshaft advanced angle.
INT/V SOL (B1)
[%] • The control value of the intake valve timing control solenoid
valve (determined by ECM according to the input signal) is in-
dicated.
• The advance angle becomes larger as the value increases
AIR COND RLY
[ON/OFF] • The air conditioner relay control condition (determined by
ECM according to the input signals) is indicated.
FUEL PUMP RLY
[ON/OFF] • Indicates the fuel pump relay control condition determined by
ECM according to the input signals.
Monitored item [Unit] Description Remarks
Page 2385 of 4331
![NISSAN LATIO 2009 Service User Guide ENGINE CONTROL SYSTEM
EC-1029
< SERVICE INFOMATION >
[MR TYPE 2] C
D E
F
G H
I
J
K L
M A EC
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The mixture ratio feedback system provides the best air/
fuel mixture ratio for drivability and emissio NISSAN LATIO 2009 Service User Guide ENGINE CONTROL SYSTEM
EC-1029
< SERVICE INFOMATION >
[MR TYPE 2] C
D E
F
G H
I
J
K L
M A EC
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The mixture ratio feedback system provides the best air/
fuel mixture ratio for drivability and emissio](/img/5/57359/w960_57359-2384.png)
ENGINE CONTROL SYSTEM
EC-1029
< SERVICE INFOMATION >
[MR TYPE 2] C
D E
F
G H
I
J
K L
M A EC
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The mixture ratio feedback system provides the best air/
fuel mixture ratio for drivability and emission control.
The three way catalyst (manifold) can then better r educe CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The
ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to EC-1210 . This maintains the mixture ratio within the range of stoichiometric
(ideal air/fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the th ree way catalyst (manifold). Even if the switching
characteristics of air fuel ratio (A/F) sensor 1 shift, the air/fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Open Loop Control The open loop system condition refers to when the ECM detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
• Deceleration and acceleration
• High-load, high-speed operation
• Malfunction of air fuel ratio (A/F) sensor 1 or its circuit
• Insufficient activation of air fuel ratio (A /F) sensor 1 at low engine coolant temperature
• High engine coolant temperature
• During warm-up
• After shifting from N to D (A/T and CVT models)
• When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL The mixture ratio feedback control system monitors the mixture ratio signal transmitted from air fuel ratio (A/F)
sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to
the theoretical mixture ratio as possible. However, the bas ic mixture ratio is not necessarily controlled as orig-
inally designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic
changes during operation (i.e., fuel injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is
then computed in terms of “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value co mpared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensati on used to maintain the mixture ratio at its theoretical
value. The signal from air fuel ratio (A/F) sensor 1 i ndicates whether the mixture ratio is RICH or LEAN com-
pared to the theoretical value. The signal then triggers a r eduction in fuel volume if the mixture ratio is rich, and
an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation ca rried out long-term to compensate for continual deviation
of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder during each engine cycl e according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System Fuel is injected simultaneously into all four cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The four fuel injectors will then receive the signals two times for each engine cycle. SEF337W