diagram INFINITI QX56 2011 Factory Repair Manual

BRC-1
BRAKES
C
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G H
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K L
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SECTION BRC
A
B
BRC
N
O P
CONTENTS
BRAKE CONTROL SYSTEM
WITH VDC
PRECAUTION ................ ...............................
5
PRECAUTIONS .............................................. .....5
Precaution for Supplemental Restraint System
(SRS) "AIR BAG" and "SEAT BELT PRE-TEN-
SIONER" ............................................................. ......
5
Precaution Necessary for Steering Wheel Rota-
tion after Battery Disconnect .....................................
5
Precaution for Procedure without Cowl Top Cover ......6
Precaution for Brake System ....................................6
Precaution for Brake Control System ........................6
Precaution for Harness Repair ..................................7
PREPARATION ............................................9
PREPARATION .............................................. .....9
Commercial Service Tools .................................. ......9
SYSTEM DESCRIPTION .............................10
COMPONENT PARTS ................................... ....10
Component Parts Location .................................. ....10
Component Description ...........................................13
ABS Actuator and Electric Unit (Control Unit) .........14
Wheel Sensor and Sensor Rotor ............................14
Stop Lamp Switch ...................................................15
Steering Angle Sensor ............................................15
Yaw Rate/Side/Decel G sensor ...............................15
Brake Fluid Level Switch .........................................15
Parking Brake Switch ..............................................15
VDC OFF Switch .....................................................15
SYSTEM .............................................................16
System Description ............................................. ....16
Fail-safe ..................................................................25
Protection Function .................................................28
VDC FUNCTION .................................................... ....28
VDC FUNCTION : System Description ...................28
TCS FUNCTION ..................................................... ....31
TCS FUNCTION : System Description ....................31
ABS FUNCTION .................................................... ....32
ABS FUNCTION : System Description ....................33
EBD FUNCTION .................................................... ....34
EBD FUNCTION : System Description ....................34
HILL START ASSIST FUNCTION ......................... ....36
hill start assist FUNCTION : System Description ....36
BRAKE LIMITED SLIP DIFFERENTIAL (BLSD)
FUNCTION ............................................................. ....
37
BRAKE LIMITED SLIP DIFFERENTIAL (BLSD)
FUNCTION : System Description ............................
37
DIAGNOSIS SYSTEM [ABS ACTUATOR
AND ELECTRIC UNIT (CONTROL UNIT)] .......
40
CONSULT-III Function ............................................40
ECU DIAGNOSIS INFORMATION ..............45
ABS ACTUATOR AND ELECTRIC UNIT
(CONTROL UNIT) .............................................
45
Reference Value .................................................. ....45
Fail-safe ...................................................................47
Protection Function ..................................................50
DTC Inspection Priority Chart ..................................50
DTC Index ...............................................................51
WIRING DIAGRAM ......................................53
BRAKE CONTROL SYSTEM ...........................53
Wiring Diagram .................................................... ....53
BASIC INSPECTION ...................................60
DIAGNOSIS AND REPAIR WORK FLOW .......60
Work Flow ............................................................ ....60
Diagnostic Work Sheet ............................................61
Revision: 2010 May2011 QX56

BRC-16
< SYSTEM DESCRIPTION >[WITH VDC]
SYSTEM
SYSTEM
System DescriptionINFOID:0000000006222569
 The system switches fluid pressure of each brake caliper to increase, to hold or to decrease according to
signals from control unit in ABS actuator and electric unit (control unit). This control system is applied to
VDC function, TCS function, ABS func tion, EBD function, hill start assist function and brake limited slip dif-
ferential (BLSD) function
 Fail-safe function is available for each function and is activated by each function when system malfunction occurs.
 The adoption of the 4WD switch assembly (4WD sh ift switch and VDC OFF switch) enables to change the
control characteristics of the VDC function, the TCS function and the brake limited slip differential (BLSD)
function into an optimal characteristics, based on a st ate of the 4WD shift switch. (Models with 4WD system)
SYSTEM DIAGRAM
NOTE:
Transfer control unit is appli ed to models with 4WD system.
INPUT SIGNAL AND OUTPUT SIGNAL
Major signal transmission between each unit via communication lines is shown in the following table.
JPFIC0182GB
Component Signal description
Yaw rate/side/decel G sensor Mainly transmits the follo
wing signals to ABS actuator and elec tric unit (control unit) via com-
munication line
*1.
 Yaw rate signal
 Side G sensor signal
 Decel G sensor signal
ECM Mainly transmits the follo
wing signals to ABS actuator and elec tric unit (control unit) via CAN
communication.
 Accelerator pedal position signal
 Engine speed signal
Mainly receives the following si gnals from ABS actuator and electr ic unit (control unit) via CAN
communication.
 Target throttle position signal
Revision: 2010 May2011 QX56

SYSTEMBRC-29
< SYSTEM DESCRIPTION > [WITH VDC]
C
D
E
G H
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K L
M A
B
BRC
N
O P
side/decel G- sensor and wheel sensor, vehicle drivi ng conditions (conditions of understeer or oversteer) are
judged and vehicle stability is improved by brake forc e control on all 4 wheels and engine output control.
 Control unit portion automatically improves driving st ability by performing brake force control as well as
engine output control, by transmitting drive signal to actuator portion according to difference between target
side slip amount and vehicle side slip amount
 VDC function can be switched to non-operational status (OFF) by operating VDC OFF switch. In this case,
VDC OFF indicator lamp turns ON.
 VDC function is not operate when 4WD mode is “4L”. (Models with 4WD system)
 VDC warning lamp blinking while VDC function is in oper ation and indicates to the driver that the function is
in operation.
 Slight vibrations are felt on the brake pedal and t he operation noises occur, when VDC function operates.
This is not a malfunction because it is caus ed by VDC function that is normally operated.
 CONSULT-III can be used to diagnose the system diagnosis.
 Fail-safe function is adopted. When a malfunction occurs in VDC function, the control is suspended for VDC
function, TCS function, hill start as sist function and brake limited slip di fferential (BLSD) function. The vehi-
cle status becomes the same as m odels without VDC function, TCS functi on, hill start assist function and
brake limited slip differential (BLSD) function. Ho wever, ABS function and EBD function are operated nor-
mally. Refer to BRC-25, "
Fail-safe".
NOTE:
VDC has the characteristic as de scribed here, but it is not the device that helps reckless driving.
SYSTEM DIAGRAM
NOTE:
Transfer control unit is applied to models with 4WD system.
INPUT SIGNAL AND OUTPUT SIGNAL
JPFIC0133GB
JPFIC0183GB
Revision: 2010 May2011 QX56

SYSTEMBRC-31
< SYSTEM DESCRIPTION > [WITH VDC]
C
D
E
G H
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K L
M A
B
BRC
N
O P
 During a cornering, brake force (brake fluid pressu re) is applied on front wheel and rear wheel on the inner
side of turn. Moment directing towards the inner side of turn is generated. Understeer is prevented.
 Applying braking during a cornering on a slippery road, when understeer tendency is judged large, engine
output is controlled as well as brake force (brake fluid pressure) of four wheels. Understeer tendency
decreases.
TCS FUNCTION
TCS FUNCTION : System DescriptionINFOID:0000000006222573
 Wheel spin status of drive wheel is detected by wheel sensor of 4
wheels. Engine output and transmission shift status is controlled
so that slip rate of drive wheels is in appropriate level. When wheel
spin occurs on drive wheel, ABS ac tuator and electric unit (control
unit) perform brake force control of LH and RH drive wheels (apply
brake force by increasing brake fluid pressure of drive wheel) and
decrease engine torque by engine torque control. Wheel spin
amount decreases. Engine torque is controlled to appropriate
level.
 TCS function can be switched to non-operational status (OFF) by
operating VDC OFF switch. In this case, VDC OFF indicator lamp
turns ON.
 TCS function is not operate when 4WD mode is “4L”. (Models with
4WD system)
 VDC warning lamp blinking while TCS function is in operation and indicates to the driver that the function is in operation.
 Slight vibrations are felt on the brake pedal and the operation noises occur, when TCS function operates. This is not a malfunc-
tion because it is caused by TCS function that is normally oper-
ated.
 CONSULT-III can be used to diagnose the system diagnosis.
 Fail-safe function is adopted. W hen a malfunction occurs in TCS
function, the control is suspended for VDC function, TCS function,
hill start assist function and brake limited slip differential (BLSD)
function. The vehicle status becomes the same as models without VDC function, TCS function, hill start
assist function and brake limited slip differential (B LSD) function. However, ABS function and EBD function
are operated normally. Refer to BRC-25, "
Fail-safe".
SYSTEM DIAGRAM
NOTE:
JPFIC0137GB
JPFIC0138GB
JPFIC0139GB
Revision: 2010 May2011 QX56

SYSTEMBRC-33
< SYSTEM DESCRIPTION > [WITH VDC]
C
D
E
G H
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K L
M A
B
BRC
N
O P
ABS FUNCTION : System DescriptionINFOID:0000000006222574
 By preventing wheel lock through brake force (brake flui d pressure) control that is electronically controlled by
detecting wheel speed during braking, stability during em ergency braking is improved so that obstacles can
be easily bypassed by steering operation.
 During braking, control units calculates wheel speed and pseudo-vehicle speed, and transmits pressure
increase, hold or decrease signals to actuator portion according to wheel slip status.
 The following effects are obtained by preventing wheel lock during
braking.
- Vehicle tail slip is prevented during braking when driving straight.
- Understeer and oversteer tendencie s are moderated during brak-
ing driving on a corner.
- Obstacles may be easily bypassed by steering operation during braking.
 Slight vibrations are felt on the brake pedal and the operation noises occur, when ABS function oper ates. This is not a malfunc-
tion because it is caused by ABS function that is normally oper-
ated.
 CONSULT-III can be used to diagnose the system diagnosis.
 Fail-safe function is adopted. When a malfunction occurs in ABS function, the control is suspended for VDC function, TCS function,
hill start assist function and brake limited slip differential (BLSD)
function. The vehicle status becomes the same as models without
VDC function, TCS function, ABS func tion, hill start assist function
and brake limited slip differential (BLSD) function. However, EBD
function is operated normally. Refer to BRC-25, "
Fail-safe".
NOTE:
 ABS has the characteristic as described here, but it is not the device that helps reckless driving.
 To stop vehicle efficiently, ABS does not operate and ordinary brake operates at low speed [approx. 5 to 10 km/h (3.1 to 6.2
MPH) or less, but differs subject to road conditions).
 Self-diagnosis is performed immediately after when engine starts and when vehicle initially is driven [by vehi-
cle speed approx. 15 km/h (9.3 MPH)]. Motor sounds are generated during self-diagnosis. In addition, brake
pedal may be felt heavy when depressing brake pedal lightly. These symptoms are not malfunctions.
SYSTEM DIAGRAM
NOTE:
JPFIC0140GB
Revision: 2010 May2011 QX56

BRC-36
< SYSTEM DESCRIPTION >[WITH VDC]
SYSTEM
SYSTEM DIAGRAM
INPUT SIGNAL AND OUTPUT SIGNAL
Major signal transmission between each unit via communication lines is shown in the following table.
hill start assist FUNCTION
hill start assist FUNCTION : System DescriptionINFOID:0000000006222576
 This function maintains brake fluid pressure so that
the vehicle does not move backwards even if brake
pedal is released to depress accelerator pedal to start the vehicle while it is stopped on an uphill slope by
depressing brake pedal.
 This function operates when the vehicle is in stop status on a uphill slope of slope ratio 10% or more and
selector lever is in the position other than P or N.
 hill start assist function is only for the start aid. It maintains the brake fluid pressure for approx. 2 seconds after releasing the brake pedal, and then decreases the pressure gradually. If the vehicle can start by the
accelerator operation, the brake is released automatically and a smooth start can be performed.
 Fail-safe function is adopted. When a malfunction occurs in hill start assist function, the control is suspended
for VDC function, TCS function, hill start assist func tion and brake limited slip differential (BLSD) function.
The vehicle status becomes the same as models without VDC function, TCS function, hill start assist func-
tion and brake limited slip differential (BLSD) functi on. However, ABS function and EBD function are oper-
ated normally. Refer to BRC-25, "
Fail-safe".
JPFIC0144GB
Component Signal description
Combination meter Mainly receives
the following signals from ABS actuator and electric unit (control unit) via CAN
communication.
 Brake warning lamp signal
Revision: 2010 May2011 QX56

SYSTEMBRC-37
< SYSTEM DESCRIPTION > [WITH VDC]
C
D
E
G H
I
J
K L
M A
B
BRC
N
O P
SYSTEM DIAGRAM
INPUT SIGNAL AND OUTPUT SIGNAL
Major signal transmission between each unit via communication lines is shown in the following table.
*: Communication line between yaw rate/side/decal G s ensor and ABS actuator and electric unit (control unit)
BRAKE LIMITED SLIP DIFFERENTIAL (BLSD) FUNCTION
BRAKE LIMITED SLIP DIFFERENTIAL (BLSD) FUNCTION : System Description
INFOID:0000000006222577
 LH and RH driving wheel spin is always monitored. If necessary, appropriate brake force is independently
applied to LH or RH driving wheel so that one-sided wheel spin is avoided and traction is maintained. Mainly
starting ability is improved.
JPFIC0145GB
Component Signal description
Yaw rate/side/decel G sensor Mainly transmits the following signals to ABS actuator and electric unit (control unit) via com-
munication line *.
 Yaw rate signal
 Side G sensor signal
 Decel G sensor signal
ECM Mainly transmits the following signals to ABS actuator and electric unit (control unit) via CAN
communication.
 Accelerator pedal position signal
 Engine speed signal
Mainly receives the following signals from ABS actuator and electric unit (control unit) via CAN
communication.
 Target throttle position signal
TCM Mainly transmits the following signals to ABS actuator and electric unit (control unit) via CAN
communication.
 Shift position signal
Combination meter Mainly receives the following signals from ABS actuator and electric unit (control unit) via CAN
communication.
 VDC warning lamp signal
 VDC OFF indicator lamp signal
Revision: 2010 May2011 QX56

BRC-38
< SYSTEM DESCRIPTION >[WITH VDC]
SYSTEM
 Brake limited slip differential (BLSD) function operates
while VDC function is in non-operational status (OFF)
by VDC OFF switch.
 VDC warning lamp blinking while brake limited slip di fferential (BLSD) function is in operation and indicates
to the driver that the function is in operation.
 Slight vibrations are felt on the brake pedal and the operation noises occur, when brake limited slip differen-
tial (BLSD) function operates. This is not a malfunction because it is caused by brake limited slip differential
(BLSD) function that is normally operated.
 Fail-safe function is adopted. When a malfunction occurs in brake limited slip differential (BLSD) function,
the control is suspended for VDC function, TCS function, hi ll start assist function and brake limited slip differ-
ential (BLSD) function. The vehicle status becomes the same as models without VDC function, TCS func-
tion, hill start assist function and brake limited slip di fferential (BLSD) function. However, ABS function and
EBD function are operated normally. Refer to BRC-25, "
Fail-safe".
SYSTEM DIAGRAM
NOTE:
Transfer control unit is applied to models with 4WD system.
INPUT SIGNAL AND OUTPUT SIGNAL
Major signal transmission between each unit via communication lines is shown in the following table.
JPFIC0183GB
Component Signal description
Yaw rate/side/decel G sensor Mainly transmits the following si
gnals to ABS actuator and electric unit (control unit) via com-
munication line
*1.
 Yaw rate signal
 Side G sensor signal
 Decel G sensor signal
ECM Mainly transmits the following si
gnals to ABS actuator and electric unit (control unit) via CAN
communication.
 Accelerator pedal position signal
 Engine speed signal
Mainly receives the following signals from ABS actuator and electric unit (control unit) via CAN
communication.
 Target throttle position signal
TCM Mainly transmits the following si
gnals to ABS actuator and electric unit (control unit) via CAN
communication.
 Shift position signal
Revision: 2010 May2011 QX56

BRAKE CONTROL SYSTEMBRC-53
< WIRING DIAGRAM > [WITH VDC]
C
D
E
G H
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K L
M A
B
BRC
N
O P
WIRING DIAGRAM
BRAKE CONTROL SYSTEM
Wiring DiagramINFOID:0000000006222584
JCFWM0627GB
Revision: 2010 May2011 QX56

BRC-54
< WIRING DIAGRAM >[WITH VDC]
BRAKE CONTROL SYSTEM
JCFWM0628GB
Revision: 2010 May2011 QX56