af mixture sensor INFINITI FX35 2005 Service Manual

EC-1
ENGINE CONTROL SYSTEM
B ENGINE
CONTENTS
C
D E
F
G H
I
J
K L
M
SECTION EC
A
EC
Revision: 2005 July 2005 FX
ENGINE CONTROL SYSTEM
VQ35DE
INDEX FOR DTC ...................................................... 15
DTC No. Index .................................................... ... 15
Alphabetical Index ............................................... ... 19
PRECAUTIONS ..................................................... ... 23
Precautions for Supplemental Restraint System
(SRS) “AIR BAG” and “SEAT BELT PRE-TEN-
SIONER” ............................................................. ... 23
On Board Diagnostic (OBD) System of Engine and
A/T ....................................................................... ... 23
Precaution ........................................................... ... 23
PREPARATION ...................................................... ... 27
Special Service Tools .......................................... ... 27
Commercial Service Tools ................................... ... 29
ENGINE CONTROL SYSTEM ............................... ... 30
System Diagram .................................................. ... 30
Multiport Fuel Injection (MFI) System ................. ... 31
Electronic Ignition (EI) System ............................ ... 33
Fuel Cut Control (at No Load and High Engine
Speed) ................................................................. ... 34
AIR CONDITIONING CUT CONTROL .................. ... 35
Input/Output Signal Chart .................................... ... 35
System Description ............................................. ... 35
AUTOMATIC SPEED CONTROL DEVICE (ASCD) ... 36
System Description ............................................. ... 36
Component Description ....................................... ... 37
CAN COMMUNICATION ....................................... ... 38
System Description ............................................. ... 38
EVAPORATIVE EMISSION SYSTEM .................... ... 39
Description .......................................................... ... 39
Component Inspection ........................................ ... 42
Removal and Installation ..................................... ... 43
How to Detect Fuel Vapor Leakage .................... ... 43
ON BOARD REFUELING VAPOR RECOVERY
(ORVR) ................................................................... ... 46
System Description ............................................. ... 46
Diagnostic Procedure .......................................... ... 47
Component Inspection ........................................ ... 49 POSITIVE CRANKCASE VENTILATION ..............
... 51
Description ........................................................... ... 51
Component Inspection ......................................... ... 51
IVIS (INFINITI VEHICLE IMMOBILIZER SYSTEM-
NATS) ..................................................................... ... 53
Description ........................................................... ... 53
ON BOARD DIAGNOSTIC (OBD) SYSTEM ......... ... 54
Introduction .......................................................... ... 54
Two Trip Detection Logic ..................................... ... 54
Emission-Related Diagnostic Information ............ ... 55
Malfunction Indicator Lamp (MIL) ........................ ... 69
OBD System Operation Chart ............................. ... 72
BASIC SERVICE PROCEDURE ............................ ... 78
Basic Inspection .................................................. ... 78
Idle Speed and Ignition Timing Check ................. ... 83
Idle Mixture Ratio Adjustment .............................. ... 85
VIN Registration .................................................. ... 96
Accelerator Pedal Released Position Learning ... ... 96
Throttle Valve Closed Position Learning .............. ... 96
Idle Air Volume Learning ..................................... ... 97
Fuel Pressure Check ........................................... ... 99
TROUBLE DIAGNOSIS ......................................... .101
Trouble Diagnosis Introduction ............................ .101
DTC Inspection Priority Chart .............................. .107
Fail-Safe Chart .................................................... .109
Symptom Matrix Chart ......................................... .110
Engine Control Component Parts Location ......... .114
Vacuum Hose Drawing ........................................ .120
Circuit Diagram .................................................... .121
ECM Harness Connector Terminal Layout .......... .123
ECM Terminals and Reference Value .................. .123
CONSULT-II Function (ENGINE) ......................... .132
Generic Scan Tool (GST) Function ...................... .144
CONSULT-II Reference Value in Data Monitor .... .147
Major Sensor Reference Graph in Data Monitor
Mode .................................................................... .151
TROUBLE DIAGNOSIS - SPECIFICATION VALUE .153
Description ........................................................... .153
Testing Condition ................................................. .153

EC-8Revision: 2005 July 2005 FX
VK45DE
INDEX FOR DTC .....................................................707
DTC No. Index ..................................................... .707
Alphabetical Index ............................................... .711
PRECAUTIONS ...................................................... .715
Precautions for Supplemental Restraint System
(SRS) “AIR BAG” and “SEAT BELT PRE-TEN-
SIONER” .............................................................. .715
On Board Diagnostic (OBD) System of Engine and
A/T ....................................................................... .715
Precaution ........................................................... .715
PREPARATION ...................................................... .719
Special Service Tools .......................................... .719
Commercial Service Tools ................................... .720
ENGINE CONTROL SYSTEM ............................... .721
System Diagram .................................................. .721
Multiport Fuel Injection (MFI) System .................. .722
Electronic Ignition (EI) System ............................ .724
Fuel Cut Control (at No Load and High Engine
Speed) ................................................................. .725
AIR CONDITIONING CUT CONTROL ................... .726
Input/Output Signal Chart .................................... .726
System Description .............................................. .726
AUTOMATIC SPEED CONTROL DEVICE (ASCD) .727
System Description .............................................. .727
Component Description ....................................... .728
CAN COMMUNICATION ........................................ .729
System Description .............................................. .729
EVAPORATIVE EMISSION SYSTEM .................... .730
Description ........................................................... .730
Component Inspection ......................................... .733
Removal and Installation ..................................... .734
How to Detect Fuel Vapor Leakage ..................... .734
ON BOARD REFUELING VAPOR RECOVERY
(ORVR) ................................................................... .737
System Description .............................................. .737
Diagnostic Procedure .......................................... .738
Component Inspection ......................................... .740
POSITIVE CRANKCASE VENTILATION .............. .742
Description ........................................................... .742
Component Inspection ......................................... .742
IVIS (INFINITI VEHICLE IMMOBILIZER SYSTEM-
NATS) ..................................................................... .744
Description ........................................................... .744
ON BOARD DIAGNOSTIC (OBD) SYSTEM ......... .745
Introduction .......................................................... .745
Two Trip Detection Logic ..................................... .745
Emission-Related Diagnostic Information ............ .746
Malfunction Indicator Lamp (MIL) ........................ .760
OBD System Operation Chart ............................. .764
BASIC SERVICE PROCEDURE ............................ .769
Basic Inspection .................................................. .769
Idle Speed and Ignition Timing Check ................. .774
Idle Mixture Ratio Adjustment .............................. .775
VIN Registration .................................................. .786
Accelerator Pedal Released Position Learning ... .786
Throttle Valve Closed Position Learning .............. .786 Idle Air Volume Learning ......................................
.787
Fuel Pressure Check ........................................... .789
TROUBLE DIAGNOSIS ......................................... .791
Trouble Diagnosis Introduction ............................ .791
DTC Inspection Priority Chart .............................. .797
Fail-Safe Chart ..................................................... .799
Symptom Matrix Chart ......................................... .800
Engine Control Component Parts Location .......... .804
Vacuum Hose Drawing ........................................ .810
Circuit Diagram .................................................... .811
ECM Harness Connector Terminal Layout ........... .813
ECM Terminals and Reference Value .................. .813
CONSULT-II Function (ENGINE) ......................... .822
Generic Scan Tool (GST) Function ...................... .835
CONSULT-II Reference Value in Data Monitor .... .838
Major Sensor Reference Graph in Data Monitor
Mode .................................................................... .842
TROUBLE DIAGNOSIS - SPECIFICATION VALUE .844
Description ........................................................... .844
Testing Condition ................................................. .844
Inspection Procedure ........................................... .844
Diagnostic Procedure ........................................... .845
TROUBLE DIAGNOSIS FOR INTERMITTENT INCI-
DENT ...................................................................... .854
Description ........................................................... .854
Diagnostic Procedure ........................................... .854
POWER SUPPLY AND GROUND CIRCUIT .......... .855
Wiring Diagram .................................................... .855
Diagnostic Procedure ........................................... .856
Ground Inspection ................................................ .861
DTC U1000, U1001 CAN COMMUNICATION LINE .862
Description ........................................................... .862
On Board Diagnosis Logic ................................... .862
DTC Confirmation Procedure ............................... .862
Wiring Diagram .................................................... .863
Diagnostic Procedure ........................................... .864
DTC P0011, P0021 IVT CONTROL ........................ .865
Description ........................................................... .865
CONSULT-II Reference Value in Data Monitor Mode .866
On Board Diagnosis Logic ................................... .866
DTC Confirmation Procedure ............................... .867
Wiring Diagram .................................................... .868
Diagnostic Procedure ........................................... .871
Component Inspection ......................................... .875
Removal and Installation ...................................... .876
DTC P0031, P0032, P0051, P0052 HO2S1 HEATER .877
Description ........................................................... .877
CONSULT-II Reference Value in Data Monitor Mode .877
On Board Diagnosis Logic ................................... .877
DTC Confirmation Procedure ............................... .878
Wiring Diagram .................................................... .879
Diagnostic Procedure ........................................... .882
Component Inspection ......................................... .884
Removal and Installation ...................................... .884
DTC P0037, P0038, P0057, P0058 HO2S2 HEATER .885
Description ........................................................... .885
CONSULT-II Reference Value in Data Monitor Mode

ENGINE CONTROL SYSTEM EC-31
[VQ35DE]
C
D E
F
G H
I
J
K L
M A
EC
Revision: 2005 July 2005 FX
Multiport Fuel Injection (MFI) SystemABS006K7
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system under normal conditions.
*2: This signal is sent to the ECM through CAN communication line.
*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). The amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air
flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated 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

High-load, high-speed operation


During deceleration

During high engine speed operation
Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS) Engine speed*
3
Piston position
Fuel injection
& mixture ratio
control Fuel injector
Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Park/neutral position (PNP) switch Gear position
Knock sensor Engine knocking condition
Battery Battery voltage*
3
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
Air conditioner switch*
2Air conditioner operation
Wheel sensor*
2Vehicle speed

EC-32
[VQ35DE]
ENGINE CONTROL SYSTEM
Revision: 2005 July 2005 FX
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst 1 can then better reduce 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-488
. 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 three way catalyst 1. Even if the switching characteris-
tics 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

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 basic 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., 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 compared 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 compensation used to maintain the mixture ratio at its theoretical
value. The signal from air fuel ratio (A/F) sensor 1 indicates whether the mixture ratio is RICH or LEAN com-
pared to the theoretical value. The signal then triggers a reduction 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 carried 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.
SEF503YB

EC-248
[VQ35DE]
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
Revision: 2005 July 2005 FX
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTIONPFP:16600
On Board Diagnosis LogicABS006OY
With the Air-Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from the air fuel ratio (A/F) sensor 1. The
ECM calculates the necessary compensation to correct the offset between the actual and the theoretical
ratios.
In case the amount of the compensation value is extremely large (the actual mixture ratio is too lean.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).
DTC Confirmation ProcedureABS006OZ
NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
WITH CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON and select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CON- SULT-II.
4. Clear the self-learning control coefficient by touching “CLEAR”.
5. Select “DATA MONITOR” mode with CONSULT-II.
6. Start engine again and let it idle for at least 10 minutes. The 1st trip DTC P0171 or P0174 should be detected at this
stage, if a malfunction exists. If so, go to EC-252, "
Diagnostic
Procedure" .
NOTE:
If 1st trip DTC is not detected during above procedure, perform-
ing the following procedure is advised.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine and drive the vehicle under the similar conditions to (1st trip) Freeze Frame Data for 10 minutes. Refer to the table below.
Hold the accelerator pedal as steady as possible.
The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following con-
ditions should be satisfied at the same time.
Sensor Input signal to ECM ECM function Actuator
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
(Mixture ratio feedback signal) Fuel injection
control Fuel injector
DTC No.Trouble diagnosis
name DTC detecting condition Possible cause
P0171
0171
(Bank 1)
Fuel injection system
too lean

Fuel injection system does not operate properly.

The amount of mixture ratio compensation is too
large. (The mixture ratio is too lean.)

Intake air leaks

Air fuel ratio (A/F) sensor 1

Fuel injector

Exhaust gas leaks

Incorrect fuel pressure

Lack of fuel

Mass air flow sensor

Incorrect PCV hose connection
P0174
0174
(Bank 2)
SEF968Y
Engine speed Engine speed in the freeze frame data ± 400 rpm
Vehicle speed Vehicle speed in the freeze frame data ± 10 km/h (6 MPH)

EC-258
[VQ35DE]
DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
Revision: 2005 July 2005 FX
DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTIONPFP:16600
On Board Diagnosis LogicABS006P2
With the Air-Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from the air fuel ratio (A/F) sensor 1. The
ECM calculates the necessary compensation to correct the offset between the actual and the theoretical
ratios.
In case the amount of the compensation value is extremely large (the actual mixture ratio is too rich.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).
DTC Confirmation ProcedureABS006P3
NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
WITH CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Turn ignition switch ON and select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CON- SULT-II.
4. Clear the self-learning control coefficient by touching “CLEAR”.
5. Select “DATA MONITOR” mode with CONSULT-II.
6. Start engine again and let it idle for at least 10 minutes. The 1st trip DTC P0172, P0175 should be detected at this stage,
if a malfunction exists. If so, go to EC-262, "
Diagnostic Proce-
dure" .
NOTE:
If 1st trip DTC is not detected during above procedure, perform-
ing the following procedure is advised.
a. Turn ignition switch OFF and wait at least 10 seconds.
b. Start engine and drive the vehicle under the similar conditions to (1st trip) Freeze Frame Data for a certain time. Refer to the table below.
Hold the accelerator pedal as steady as possible.
The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following con-
ditions should be satisfied at the same time.
7. If it is difficult to start engine at step 6, the fuel injection system has a malfunction, too.
Sensor Input signal to ECM ECM function Actuator
Air fuel ration (A/F) sensor 1 Density of oxygen in exhaust gas
(Mixture ratio feedback signal) Fuel injection
control Fuel injector
DTC No.Trouble diagnosis
name DTC detecting condition Possible cause
P0172
0172
(Bank 1) Fuel injection system
too rich

Fuel injection system does not operate properly.

The amount of mixture ratio compensation is too
large. (The mixture ratio is too rich.)

Air fuel ratio (A/F) sensor 1

Fuel injector

Exhaust gas leaks

Incorrect fuel pressure

Mass air flow sensor
P0175
0175
(Bank 2)
SEF968Y
Engine speed Engine speed in the freeze frame data ± 400 rpm
Vehicle speed Vehicle speed in the freeze frame data ± 10 km/h (6 MPH)
Engine coolant temperature
(T) condition When the freeze frame data shows lower than 70
°C (158 °F),
T should be lower than 70 °C (158 °F).
When the freeze frame data shows higher than or equal to 70 °C (158 °F),
T should be higher than or equal to 70 °C (158 °F).

EC-336
[VQ35DE]
DTC P0444, P0445 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
Revision: 2005 July 2005 FX
DTC P0444, P0445 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID
VA LV E
PFP:14920
DescriptionABS006QT
SYSTEM DESCRIPTION
*1: ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to the ECM through CAN communication line.
This system controls flow rate of fuel vapor from the EVAP canister. The opening of the vapor by-pass pas-
sage in the EVAP canister purge volume control solenoid valve changes to control the flow rate. The EVAP
canister purge volume control solenoid valve repeats ON/OFF operation according to the signal sent from the
ECM. The opening of the valve varies for optimum engine control. The optimum value stored in the ECM is
determined by considering various engine conditions. When the engine is operating, the flow rate of fuel vapor
from the EVAP canister is regulated as the air flow changes.
COMPONENT DESCRIPTION
The EVAP canister purge volume control solenoid valve uses a ON/
OFF duty to control the flow rate of fuel vapor from the EVAP canis-
ter. The EVAP canister purge volume control solenoid valve is
moved by ON/OFF pulses from the ECM. The longer the ON pulse,
the greater the amount of fuel vapor that will flow through the valve.
CONSULT-II Reference Value in Data Monitor ModeABS006QU
Specification data are reference values.
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed*
1
EVAP canister
purge flow control EVAP canister purge vol-
ume control solenoid valve
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Battery Battery voltage*
1
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
(Mixture ratio feedback signal)
Fuel tank temperature sensor Fuel temperature in fuel tank
Wheel sensor*
2Vehicle speed
SEF337U
MONITOR ITEM CONDITION SPECIFICATION
PURG VOL C/V

Engine: After warming up

Selector lever: P or N

Air conditioner switch: OFF

No-load Idle
(Accelerator pedal is not depressed
even slightly, after engine starting) 0%
2,000 rpm —

EC-560
[VQ35DE]
DTC P1444 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
Revision: 2005 July 2005 FX
DTC P1444 EVAP CANISTER PURGE VOLUME CONTROL SOLENOID VALVE
PFP:14920
DescriptionABS006VU
SYSTEM DESCRIPTION
*1: ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to the ECM through CAN communication line.
This system controls flow rate of fuel vapor from the EVAP canister. The opening of the vapor by-pass pas-
sage in the EVAP canister purge volume control solenoid valve changes to control the flow rate. The EVAP
canister purge volume control solenoid valve repeats ON/OFF operation according to the signal sent from the
ECM. The opening of the valve varies for optimum engine control. The optimum value stored in the ECM is
determined by considering various engine conditions. When the engine is operating, the flow rate of fuel vapor
from the EVAP canister is regulated as the air flow changes.
COMPONENT DESCRIPTION
The EVAP canister purge volume control solenoid valve uses a ON/
OFF duty to control the flow rate of fuel vapor from the EVAP canis-
ter. The EVAP canister purge volume control solenoid valve is
moved by ON/OFF pulses from the ECM. The longer the ON pulse,
the greater the amount of fuel vapor that will flow through the valve.
CONSULT-II Reference Value in Data Monitor ModeABS006VV
Specification data are reference values.
Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE) Engine speed*
1
EVAP canister
purge flow control EVAP canister purge vol-
ume control solenoid valve
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Battery Battery voltage*
1
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
(Mixture ratio feedback signal)
Fuel tank temperature sensor Fuel temperature in fuel tank
Wheel sensor*
2Vehicle speed
SEF337U
MONITOR ITEM CONDITION SPECIFICATION
PURG VOL C/V

Engine: After warming up

Selector lever: P or N

Air conditioner switch: OFF

No-load Idle
(Accelerator pedal is not depressed
even slightly, after engine starting) 0%
2,000 rpm —

EC-722
[VK45DE]
ENGINE CONTROL SYSTEM
Revision: 2005 July 2005 FX
Multiport Fuel Injection (MFI) SystemABS00E3Y
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system under normal conditions.
*2: This signal is sent to the ECM through CAN communication line.
*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). The amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from the 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 compensated 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

High-load, high-speed operation


During deceleration

During high engine speed operation
Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS) Engine speed*
3
Piston position
Fuel injection
& mixture ratio
control Fuel injector
Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Heated oxygen sensor 1 Density of oxygen in exhaust gas
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Park/neutral position (PNP) switch Gear position
Battery Battery voltage*
3
Knock sensor Engine knocking condition
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
ABS actuator and electric unit (control unit)*
2VDC/TCS operation command
Air conditioner switch*
2Air conditioner operation
Wheel sensor*
2Vehicle speed

ENGINE CONTROL SYSTEM EC-723
[VK45DE]
C
D E
F
G H
I
J
K L
M A
EC
Revision: 2005 July 2005 FX
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
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 reduce CO, HC and NOx emissions. This system uses
heated oxygen 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
heated oxygen sensor 1, refer to EC-935
. 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 three way catalyst (manifold). Even if the switching
characteristics of heated oxygen 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 heated oxygen sensor 1 or its circuit

Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature

High engine coolant temperature

During warm-up

After shifting from N to D

When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from heated oxygen
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 basic 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., 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 compared 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 compensation used to maintain the mixture ratio at its theoretical
value. The signal from heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared
to the theoretical value. The signal then triggers a reduction 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 carried 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.
PBIB0121E