Nissan Pathfinder (2012 year). Manual — part 246
MULTIPORT FUEL INJECTION SYSTEM
EC-49
< SYSTEM DESCRIPTION >
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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 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
. 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 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., 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 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 overtime to compensate for continual deviation of
the short-term fuel trim from the central value. Continual deviation will occur due to individual engine differ-
ences, wear over time and changes in the usage environment.
PBIB3020E
August 2012
2012 Pathfinder
EC-50
< SYSTEM DESCRIPTION >
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MULTIPORT FUEL INJECTION SYSTEM
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder during each engine cycle 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 six cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The six fuel injectors will then receive the signals two times for each engine cycle.
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.
SEF179U
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2012 Pathfinder
ELECTRIC IGNITION SYSTEM
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< SYSTEM DESCRIPTION >
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ELECTRIC IGNITION SYSTEM
System Description
INFOID:0000000007357959
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
Firing order: 1-2-3-4-5-6
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 injection pulse width and camshaft position sensor (PHASE) sig-
nal. Computing this information, ignition signals are transmitted to the power transistor.
During the following conditions, the ignition timing is revised 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.
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
Knock sensor
Engine knocking
TCM
Gear position
Battery
Battery voltage*
2
Wheel sensor
Vehicle speed*
1
August 2012
2012 Pathfinder
EC-52
< SYSTEM DESCRIPTION >
[VQ40DE]
AIR CONDITIONING CUT CONTROL
AIR CONDITIONING CUT CONTROL
Input/Output Signal Chart
INFOID:0000000007357960
*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
INFOID:0000000007357961
This system improves engine operation when the air conditioner is used.
Under the following conditions, the air conditioner is turned off.
• When the accelerator pedal is fully depressed.
• When cranking the engine.
• At high engine speeds.
• When the engine coolant temperature becomes excessively high.
• When operating power steering during low engine speed or low vehicle speed.
• When engine speed is excessively low.
• When refrigerant pressure is excessively low or high.
Sensor
Input Signal to ECM
ECM function
Actuator
Air conditioner switch
Air conditioner ON signal*
1
Air conditioner
cut control
Air conditioner relay
Accelerator pedal position sensor
Accelerator pedal position
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)
Engine speed*
2
Engine coolant temperature sensor
Engine coolant temperature
Battery
Battery voltage*
2
Refrigerant pressure sensor
Refrigerant pressure
Power steering pressure sensor
Power steering operation
Wheel sensor
Vehicle speed*
1
August 2012
2012 Pathfinder
AUTOMATIC SPEED CONTROL DEVICE (ASCD)
EC-53
< SYSTEM DESCRIPTION >
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
System Description
INFOID:0000000007357962
INPUT/OUTPUT SIGNAL CHART
*: This signal is sent to the ECM via the CAN communication line.
BASIC ASCD SYSTEM
Refer to Owner's Manual for ASCD operating instructions.
Automatic Speed Control Device (ASCD) allows a driver to keep vehicle at predetermined constant speed
without depressing accelerator pedal. Driver can set vehicle speed in advance between approximately 40 km/
h (25 MPH) and 144 km/h (89 MPH).
ECM controls throttle angle of electric throttle control actuator to regulate engine speed.
Operation status of ASCD is indicated by CRUISE indicator and SET indicator in combination meter. If any
malfunction occurs in the ASCD system, it automatically deactivates control.
NOTE:
Always drive vehicle in a safe manner according to traffic conditions and obey all traffic laws.
SET OPERATION
Press MAIN switch. (The CRUISE indicator in combination meter illuminates.)
When vehicle speed reaches a desired speed between approximately 40 km/h (25 MPH) and 144 km/h (89
MPH), press SET/COAST switch. (Then SET indicator in combination meter illuminates.)
ACCELERATE OPERATION
If the RESUME/ACCELERATE switch is pressed during cruise control driving, increase the vehicle speed until
the switch is released or vehicle speed reaches maximum speed controlled by the system.
And then ASCD will maintain the new set speed.
CANCEL OPERATION
When any of following conditions exist, cruise operation will be canceled.
• CANCEL switch is pressed
• More than 2 switches on ASCD steering switch are pressed at the same time (Set speed will be cleared)
• Brake pedal is depressed
• Selector lever position is changed to N, P or R
• Vehicle speed decreased to 13 km/h (8 MPH) lower than the set speed
• VDC system is operated
When the ECM detects any of the following conditions, the ECM will cancel the cruise operation and inform
the driver by blinking indicator lamp.
• Engine coolant temperature is slightly higher than the normal operating temperature, CRUISE lamp may
blink slowly.
When the engine coolant temperature decreases to the normal operating temperature, CRUISE lamp will
stop blinking and the cruise operation will be able to work by depressing SET/COAST switch or RESUME/
ACCELERATE switch.
• Malfunction for some self-diagnoses regarding ASCD control: SET lamp will blink quickly.
If MAIN switch is turned to OFF while ASCD is activated, all of ASCD operations will be canceled and vehicle
speed memory will be erased.
COAST OPERATION
When the SET/COAST switch is pressed during cruise control driving, decrease vehicle set speed until the
switch is released. And then ASCD will maintain the new set speed.
RESUME OPERATION
Sensor
Input signal to ECM
ECM function
Actuator
ASCD brake switch
Brake pedal operation
ASCD vehicle speed control
Electric throttle control
actuator
Stop lamp switch
Brake pedal operation
ASCD steering switch
ASCD steering switch operation
TCM
Gear position
Wheel sensor
Vehicle speed*
TCM
Powertrain revolution*
August 2012
2012 Pathfinder
EC-54
< SYSTEM DESCRIPTION >
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AUTOMATIC SPEED CONTROL DEVICE (ASCD)
When the RESUME/ACCELERATE switch is pressed after canceling operation other than depressing the
MAIN switch, vehicle speed will return to last set speed. To resume vehicle set speed, vehicle condition must
meet following conditions.
• Brake pedal is released
• Selector lever position is in other than P and N
• Vehicle speed is greater than 40 km/h (25 MPH) and less than 144 km/h (89 MPH)
Component Description
INFOID:0000000007357963
ASCD STEERING SWITCH
ASCD BRAKE SWITCH
STOP LAMP SWITCH
ELECTRIC THROTTLE CONTROL ACTUATOR
ASCD INDICATOR
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2012 Pathfinder
CAN COMMUNICATION
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< SYSTEM DESCRIPTION >
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CAN COMMUNICATION
System Description
INFOID:0000000007357964
CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle mul-
tiplex communication line with high data communication speed and excellent error detection ability. Many elec-
tronic control units are equipped onto a vehicle, and each control unit shares information and links with other
control units during operation (not independent). In CAN communication, control units are connected with 2
communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only.
LAN-52, "CAN System Specification Chart"
, about CAN communication for detail.
August 2012
2012 Pathfinder
EC-56
< SYSTEM DESCRIPTION >
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COOLING FAN CONTROL
COOLING FAN CONTROL
Description
INFOID:0000000007357965
SYSTEM DESCRIPTION
Cooling Fan Control
*1: The ECM determines the start signal status by the signals of engine speed and battery voltage.
*2: This signal is sent to ECM via the CAN communication line.
The ECM controls the cooling fan corresponding to the vehicle speed, engine coolant temperature, refrigerant
pressure, and air conditioner ON signal. The control system has 3-step control [HIGH/LOW/OFF].
Cooling Fan Operation
Cooling Fan Relay Operation
The ECM controls cooling fan relays in the IPDM E/R via the CAN communication line.
Sensor
Input Signal to ECM
ECM function
Actuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)
Engine speed*
1
Cooling fan
control
IPDM E/R
(Cooling fan relays)
Battery
Battery voltage*
1
Wheel sensor
Vehicle speed*
2
Engine coolant temperature sensor
Engine coolant temperature
Air conditioner switch
Air conditioner ON signal*
2
Refrigerant pressure sensor
Refrigerant pressure
PBIB2531E
Cooling fan speed
Cooling fan relay
LO
HI
Stop (OFF)
OFF
OFF
Low (LOW)
ON
OFF
High (HI)
ON
ON
August 2012
2012 Pathfinder
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