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Nissan Pathfinder (2012 year). Manual - part 303

ENGINE CONTROL SYSTEM

EC-505

< SYSTEM DESCRIPTION >

[VK56DE]

ASCD steering switch

MAIN switch

CANCEL switch

SET/COAST switch

RESUME/ACCELERATE switch

ECM harness connectors (view with
ECM cover removed)

Coolant reservoir

Accelerator pedal position sensor

Fuel level sensor unit and fuel pump
harness connector (view with fuel
tank removed)

AWBIA0084ZZ

August 2012

2012 Pathfinder

EC-506

< SYSTEM DESCRIPTION >

[VK56DE]

ENGINE CONTROL SYSTEM

10. Fuel pump, fuel level sensor unit and

fuel filter

11. Fuel pressure regulator

12. ASCD brake switch

13. Stop lamp switch

14. Brake pedal

August 2012

2012 Pathfinder

MULTIPORT FUEL INJECTION SYSTEM

EC-507

< SYSTEM DESCRIPTION >

[VK56DE]

MULTIPORT FUEL INJECTION SYSTEM

System Description

INFOID:0000000007358425

INPUT/OUTPUT SIGNAL CHART

*1: This sensor is not used to control the engine system. This is used only for the on board diagnosis.
*2: This signal is sent to the ECM via the 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, the camshaft 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 position 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*

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

Knock sensor

Engine knocking condition

Battery

Battery voltage*

Power steering pressure sensor

Power steering operation

Heated oxygen sensor 2*

Density of oxygen in exhaust gas

ABS actuator and electric unit (control unit)

VDC/TCS operation command*

Air conditioner switch

Air conditioner operation*

Unified meter control unit

Gear position

Vehicle speed*

August 2012

2012 Pathfinder

EC-508

< SYSTEM DESCRIPTION >

[VK56DE]

MULTIPORT FUEL INJECTION SYSTEM

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 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 A/F

sensor 1, refer to

EC-676, "Component Description"

. This maintains the mixture ratio within the range of sto-

ichiometric (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 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 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

• 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 controls the basic mixture ratio as close to the theoret-

ical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally

designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes dur-

ing 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 A/F sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the the-

oretical 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

MULTIPORT FUEL INJECTION SYSTEM

EC-509

< SYSTEM DESCRIPTION >

[VK56DE]

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 ignition order. This system is used

when the engine is running.

Simultaneous Multiport Fuel Injection System

Fuel is injected simultaneously into all 8 cylinders twice each engine cycle. In other words, pulse signals of the

same width are simultaneously transmitted from the ECM.

The 8 fuel injectors will then receive the signals 2 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 speed.

PBIB0122E

August 2012

2012 Pathfinder

EC-510

< SYSTEM DESCRIPTION >

[VK56DE]

ELECTRIC IGNITION SYSTEM

ELECTRIC IGNITION SYSTEM

System Description

INFOID:0000000007358426

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 - 8 - 7 - 3 - 6 - 5 - 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 injection pulse width and camshaft position sensor signal. Comput-

ing 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*

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

Battery

Battery voltage*

Unified meter control unit

Gear position

Vehicle speed*

August 2012

2012 Pathfinder

AIR CONDITIONING CUT CONTROL

EC-511

< SYSTEM DESCRIPTION >

[VK56DE]

AIR CONDITIONING CUT CONTROL

Input/Output Signal Chart

INFOID:0000000007358427

*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:0000000007358428

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*

Air conditioner
cut control

Air conditioner relay

Accelerator pedal position sensor

Accelerator pedal position

Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)

Engine speed*

Engine coolant temperature sensor

Engine coolant temperature

Battery

Battery voltage*

Refrigerant pressure sensor

Refrigerant pressure

Power steering pressure sensor

Power steering operation

Unified meter control unit

Vehicle speed*

August 2012

2012 Pathfinder

EC-512

< SYSTEM DESCRIPTION >

[VK56DE]

AUTOMATIC SPEED CONTROL DEVICE (ASCD)

AUTOMATIC SPEED CONTROL DEVICE (ASCD)

System Description

INFOID:0000000007358429

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 on combination meter. If any

malfunction occurs in ASCD system, CRUISE indicator blinks and ASCD control is deactivated.

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 on 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 on 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 at 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, R position

• 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 CRUISE indicator.

• Engine coolant temperature is slightly higher than the normal operating temperature, CRUISE indicator may

blink slowly.

When the engine coolant temperature decreases to the normal operating temperature, CRUISE indicator will

stop blinking and the cruise operation will be able to work by pressing SET/COAST switch or RESUME/

ACCELERATE switch.

• Malfunction for some self-diagnoses regarding ASCD control: SET indicator 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

Unified meter control unit

Gear position

Vehicle speed*

TCM

Powertrain revolution*

August 2012

2012 Pathfinder

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