INFINITI QX56 2007 Factory Service Manual

EC-18
< SERVICE INFORMATION >
PRECAUTIONS
•Do not disassemble ECM.
•If a battery cable is disconnected, the memory will return to
the ECM value.
The ECM will now start to self-control at its initial value.
Engine operation can vary slightly when the terminal is dis-
connected. However, this is not an indication of a malfunc-
tion. Do not replace parts because of a slight variation.
•If the battery is disconnected, the following emission-related
diagnostic information will be lost within 24 hours.
-Diagnostic trouble codes
-1st trip diagnostic trouble codes
-Freeze frame data
-1st trip freeze frame data
-System readiness test (SRT) codes
-Test values
•When connecting ECM harness connector, fasten it securely
with a lever as far as it will go as shown in the figure.
•When connecting or disconnecting pin connectors into or
from ECM, take care not to damage pin terminals (bend or
break).
Make sure that there are not any bends or breaks on ECM pin
terminal, when connecting pin connectors.
•Securely connect ECM harness connectors.
A poor connection can cause an extremely high (surge) volt-
age to develop in coil and condenser, thus resulting in dam-
age to ICs.
•Keep engine control system harness at least 10 cm (4 in) away
from adjacent harness, to prevent engine control system mal-
functions due to receiving external noise, degraded operation
of ICs, etc.
•Keep engine control system parts and harness dry.
•Before replacing ECM, perform ECM Terminals and Reference
Value inspection and make sure ECM functions properly.
Refer to EC-103, "
ECM Terminal and Reference Value" .
•Handle mass air flow sensor carefully to avoid damage.
•Do not disassemble mass air flow sensor.
•Do not clean mass air flow sensor with any type of detergent.
•Do not disassemble electric throttle control actuator.
•Even a slight leak in the air intake system can cause serious
incidents.
•Do not shock or jar the camshaft position sensor (PHASE),
crankshaft position sensor (POS).
PBIB1164E
BBIA0387E
PBIB0090E
MEF040D

PRECAUTIONS
EC-19
< SERVICE INFORMATION >
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•After performing each TROUBLE DIAGNOSIS, perform DTC
Confirmation Procedure or Overall Function Check.
The DTC should not be displayed in the DTC Confirmation
Procedure if the repair is completed. The Overall Function
Check should be a good result if the repair is completed.
•When measuring ECM signals with a circuit tester, never allow
the two tester probes to contact.
Accidental contact of probes will cause a short circuit and
damage the ECM power transistor.
•Do not use ECM ground terminals when measuring input/out-
put voltage. Doing so may result in damage to the ECM's tran-
sistor. Use a ground other than ECM terminals, such as the
ground.
•B1 indicates the bank 1, B2 indicates the bank 2 as shown in
the figure.
SEF217U
SEF348N
PBIB1144E

EC-20
< SERVICE INFORMATION >
PRECAUTIONS
•Do not operate fuel pump when there is no fuel in lines.
•Tighten fuel hose clamps to the specified torque.
•Do not depress accelerator pedal when starting.
•Immediately after starting, do not rev up engine unnecessar-
ily.
•Do not rev up engine just prior to shutdown.
•When installing C.B. ham radio or a mobile phone, be sure to
observe the following as it may adversely affect electronic
control systems depending on installation location.
-Keep the antenna as far as possible from the electronic con-
trol units.
-Keep the antenna feeder line more than 20 cm (8 in) away
from the harness of electronic controls.
Do not let them run parallel for a long distance.
-Adjust the antenna and feeder line so that the standing-wave
radio can be kept smaller.
-Be sure to ground the radio to vehicle body.
BBIA0402E
SEF709Y
SEF708Y

PREPARATION
EC-21
< SERVICE INFORMATION >
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PREPARATION
Special Service ToolINFOID:0000000003531583
The actual shapes of Kent-Moore tools may differ from those of special service tools illustrated here.
Tool number
(Kent-Moore No.)
Tool nameDescription
EG17650301
(J-33984-A)
Radiator cap tester
adapterAdapting radiator cap tester to radiator cap and ra-
diator filler neck
a: 28 (1.10) dia.
b: 31.4 (1.236) dia.
c: 41.3 (1.626) dia.
Unit: mm (in)
KV10117100
(J-36471-A)
Heated oxygen sensor
wrenchLoosening or tightening heated oxygen sensors
with 22 mm (0.87 in) hexagon nut
KV10114400
(J-38365)
Heated oxygen sensor
wrenchLoosening or tightening heated oxygen sensors
a: 22 mm (0.87 in)
(J-44626)
Air fuel ratio (A/F) sen-
sor wrenchLoosening or tightening air fuel ratio (A/F) sensor 1
(J-44321)
Fuel pressure gauge
kitChecking fuel pressure
(J-44321-6)
Fuel pressure adapterConnecting fuel pressure gauge to quick connec-
tor type fuel lines.
S-NT564
S-NT379
S-NT636
LEM054
LEC642
LBIA0376E

EC-22
< SERVICE INFORMATION >
PREPARATION
Commercial Service Tool
INFOID:0000000003531584
(J-45488)
Quick connector re-
leaseRemove fuel tube quick connectors in engine
room.
(J-23688)
Engine coolant refrac-
tometerChecking concentration of ethylene glycol in en-
gine coolant Tool number
(Kent-Moore No.)
Tool nameDescription
PBIC0198E
WBIA0539E
Tool name
(Kent-Moore No.)Description
Leak detector
i.e.: (J-41416)Locating the EVAP leak
EVAP service port
adapter
i.e.: (J-41413-OBD)Applying positive pressure through EVAP service
port
Fuel filler cap adapter
i.e.: (MLR-8382)Checking fuel tank vacuum relief valve opening
pressure
Socket wrench Removing and installing engine coolant tempera-
ture sensor
S-NT703
S-NT704
S-NT815
S-NT705

PREPARATION
EC-23
< SERVICE INFORMATION >
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Oxygen sensor thread
cleaner
i.e.: (J-43897-18)
(J-43897-12)Reconditioning the exhaust system threads before
installing a new oxygen sensor. Use with anti-
seize lubricant shown below.
a: 18 mm diameter with pitch 1.5 mm for Zirco-
nia Oxygen Sensor
b: 12 mm diameter with pitch 1.25 mm for Tita-
nia Oxygen Sensor
Anti-seize lubricant
i.e.: (Permatex
TM
133AR or equivalent
meeting MIL specifica-
tion MIL-A-907)Lubricating oxygen sensor thread cleaning tool
when reconditioning exhaust system threads. Tool name
(Kent-Moore No.)Description
AEM488
S-NT779

EC-24
< SERVICE INFORMATION >
ENGINE CONTROL SYSTEM
ENGINE CONTROL SYSTEM
SchematicINFOID:0000000003531585
Multiport Fuel Injection (MFI) SystemINFOID:0000000003531586
INPUT/OUTPUT SIGNAL CHART
PBIB3438E

ENGINE CONTROL SYSTEM
EC-25
< SERVICE INFORMATION >
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*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 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
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor (POS)
Engine speed*
3
Piston position
Fuel injection
& mixture ratio
controlFuel 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
ABS actuator and electric unit (control unit)
VDC/TCS operation command*
2
Air conditioner switch
Air conditioner operation*2
Wheel sensor
Vehicle speed*2
PBIB3020E

EC-26
< SERVICE INFORMATION >
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 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-225
. 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 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 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 eight cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The eight fuel injectors will then receive the signals two times for each engine cycle.
PBIB0122E

ENGINE CONTROL SYSTEM
EC-27
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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 speed.
Electronic Ignition (EI) SystemINFOID:0000000003531587
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 - 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.
Fuel Cut Control (at No Load and High Engine Speed)INFOID:0000000003531588
INPUT/OUTPUT SIGNAL CHART
*: This signal is sent to the ECM through CAN communication line.Sensor Input signal to ECM ECM function Actuator
Crankshaft position sensor (POS)
Engine speed*
2
Piston position
Ignition timing
controlPower 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
Park/neutral position (PNP) switch Gear position
Battery
Battery voltage*
2
Wheel sensor
Vehicle speed*1
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
Wheel sensor Vehicle speed*