Nissan X-Trail 32. Manual - part 834

SYSTEM

EC-465

< SYSTEM DESCRIPTION >

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“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 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 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 four cylinders twice each engine cycle. In other words, pulse signals
of the same width are simultaneously transmitted from the ECM.
The four 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.

ELECTRIC IGNITION SYSTEM

ELECTRIC IGNITION SYSTEM : System Description

INFOID:0000000010986234

SYSTEM DIAGRAM

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.

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EC-466

< SYSTEM DESCRIPTION >

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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.

INTAKE VALVE TIMING CONTROL

INTAKE VALVE TIMING CONTROL : System Description

INFOID:0000000010986235

INTAKE VALVE TIMING CONTROL

System Diagram

System Description

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SYSTEM

EC-467

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This mechanism hydraulically controls cam phases continuously with the fixed operating angle of the intake
valve.
The ECM receives signals such as crankshaft position, camshaft position, engine speed, and engine coolant
temperature. Then, the ECM sends ON/OFF pulse duty signals to the intake valve timing (IVT) control sole-
noid valve depending on driving status. This makes it possible to control the shut/open timing of the intake
valve to increase engine torque in low/mid speed range and output in high-speed range.

INTAKE VALVE TIMING INTERMEDIATE LOCK CONTROL

System Diagram

System Description

The intake valve timing intermediate lock control improves the cleaning ability of exhaust gas at cold starting
by fixing the camshaft sprocket (INT) with two lock keys and bringing the cam phase into intermediate phase.

Cam phase is fixed at the intermediate phase by two lock keys in the camshaft sprocket (INT). Lock key 1 con-
trols retard position and lock key 2 controls advance position.
ECM controls the intermediate phase lock by opening/closing the intake valve timing intermediate lock control
solenoid valve to control oil pressure acting on the lock key and locking/unlocking the lock key.

Lock/Unlock Activation

When ECM activates the intake valve timing intermediate lock control solenoid valve, oil pressure generated in
the oil pump is drained through the oil pressure path in the control valve. Since oil pressure is not acted on the
lock key, the lock key position is fixed by the spring tension and the cam phase is fixed at the intermediate
phase.
When ECM deactivates the intake valve timing intermediate lock control solenoid valve, unlocking oil pressure
acts on each lock key. Lock key 1 is not released because it is under load due to sprocket rotational force. For

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EC-468

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this reason, lock key 2 is released first by being pushed up by unlocking oil pressure. When lock key 2 is
released, some clearance is formed between lock key 1 and the rotor due to sprocket rotational force and
return spring force. Accordingly, lock key 1 is pushed up by unlocking oil pressure and the intermediated
phase lock is released.

When stopping the engine

When the ignition switch is turned from idle state to OFF, ECM receives an ignition switch signal from BCM via
CAN communication and activates the intake valve timing intermediate lock control solenoid valve and drains
oil pressure acting on the lock key before activating the intake valve timing control solenoid valve and operat-
ing the cam phase toward the advance position.
The cam phase is fixed by the lock key when shifting to the intermediated phase and ECM performs Lock
judgment to stop the engine.

When starting the engine

When starting the engine by cold start, ECM judges the locked/unlocked state when ignition switch is turned
ON. When judged as locked state (fixed at the intermediate phase), the intake valve timing intermediate lock
control solenoid valve is activated. Since oil pressure does not act on the lock key even when the engine is
started, the cam phase is fixed at the intermediate phase and the intake valve timing control is not performed.
When the engine stops without locking the cam phase at the intermediate phase due to an engine stall and the
state is not judged as locked, the intake valve timing intermediate lock control solenoid valve and the intake
valve timing control solenoid valve are activated and the cam phase shifts to the advanced position to be
locked at the intermediate phase. Even when not locked in the intermediate lock phase due to no oil pressure
or low oil pressure, a ratchet structure of the camshaft sprocket (INT) rotor allows the conversion to the inter-
mediate phase in stages by engine vibration.
When engine coolant temperature is more than 60

°

C, the intake valve timing is controlled by deactivating the

intake valve timing intermediate lock control solenoid valve and releasing the intermediate phase lock.
When the engine is started after warming up, ECM releases the intermediate phase lock immediately after the
engine start and controls the intake valve timing.

EXHAUST VALVE TIMING CONTROL

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