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Infiniti Q45 (FY33). Manual - part 79

System Components

SBR619DA

Component parts

Description

Wheel sensor

Senses or detects each wheel rotation speed.

ABS/TCS control unit

Receives signals from all wheel sensors and sends a control signal to TAC module, ECM and TCM.
If electrical system becomes inoperative, fail-safe function will activate, operating the vehicle similar
to a vehicle which is not equipped with TCS.
When fail-safe function activates, TCS OFF indicator and TCS SLIP indicator light. These indicators
are located in the meter cluster. The self-diagnostic function supports the CONSULT-II. The self-
diagnostic result is also indicated by the SLIP indicator.

TAC module

Receives a signal from ABS/TCS control unit in order to control throttle actuator. Throttle motor
operation will then be controlled for regulating throttle positioning.
If throttle motor control system becomes inoperative, throttle motor operation will be suspended.
TAC module will then activate fail-safe function. The self-diagnostic result is indicated by the control
unit LED. The self-diagnostic function supports the CONSULT-II.

Throttle actuator

Receives a signal from TAC module and activates throttle motor.

ECM

Receives a signal from ABS/TCS control unit and provides fuel-cut control. This in turn regulates
engine drive torque.

TCM

Receives a signal from ABS/TCS control unit and provides shifting control.

SLIP indicator

Lights in conjunction with TCS operation. Also indicates self-diagnostic result for TCS.

TCS OFF indicator

Lights when TCS is “OFF” (TCS switch “ON”), indicating that TCS is not operating.

TCS OFF switch

Set to “ON” to deactivate TCS.

IDX

TRACTION CONTROL SYSTEM — TCS —

BR-33

ABS (Anti-lock brake system) Operation

When the vehicle speed is less than 10 km/h (6 MPH) this system does not work.

The Anti-Lock Brake System (ABS) has a self-test function. The system turns on the ABS warning lamp
for 1 second each time the ignition switch is turned “ON”. After the engine is started, the ABS warning lamp
turns off. The system performs a test the first time the vehicle reaches 6 km/h (4 MPH). A mechanical noise
may be heard as the ABS performs this self-test. This is a normal part of the self-test feature. If a mal-
function is found during this check, the ABS warning lamp will stay on.

While driving, a mechanical noise may be heard during ABS operation. This is a normal condition.

ABS Hydraulic Circuit

SBR413E

Inlet solenoid valve

Outlet solenoid valve

Reservoir

Pump

Motor

Inlet valve

Outlet valve

Bypass check valve

Damper

TRACTION CONTROL SYSTEM — TCS —

BR-34

TCS (Traction Control System) Operation

This system has a secondary throttle valve which is opened/closed by a throttle motor. This is in addition to
the primary throttle valve linked to the accelerator pedal. The opening angle of this valve is feed-back con-
trolled by the secondary throttle sensor.
The secondary throttle valve is normally kept in the fully opened position. When a slip of the drive wheels is
detected by the wheel sensor, the TCS control unit determines the optimum opening position of the second-
ary throttle valve. The Throttle Actuator Control (TAC) Module then closes the secondary throttle valve to the
correct position according to this information. It then reduces the engine output torque, and so avoids occur-
rence of slip. At the same time, a signal sent from the TCS control unit allows the ECM to cut fuel supply. The
TCS control unit needs the primary throttle valve position signal to determine the secondary throttle valve
opening position. The TAC module receives the throttle sensor position signal through the ECM, and the TAC
module sends the signal to the TCS control unit.
If the TAC module detects trouble in the throttle valve control system, it de-energizes a relay located up-stream
of the throttle motor power supply. The secondary throttle valve is then opened fully by means of a return
spring. In this case, ordinary vehicle operation is assured by the functioning of the primary throttle valve. At
the same time, the TAC module stops sending the throttle position sensor signal to the TCS control unit.

Throttle Control + Engine Control TCS System
Configuration (Tandem Throttle System)

SBR620DB

IDX

TRACTION CONTROL SYSTEM — TCS —

BR-35

SBR621DA

Secondary Throttle Fully-closed Position Self-
learning Control

When a certain condition occurs with ignition switch ON, the TAC
module checks for operation of the throttle control system. It does
this by fully closing the secondary throttle and then opening it fully.
Simultaneously, the TAC module reads the secondary throttle posi-
tion sensor output values at both the fully closed/opened positions.
This data is used for self-diagnosing the secondary throttle driving
system. The same data is also used for improving the control accu-
racy of the secondary throttle.
This learning control is performed at the moment the ignition switch
is turned ON under conditions: Automatic transmission is set in “N”
or “P” position; Accelerator pedal is released completely.

TRACTION CONTROL SYSTEM — TCS —

BR-36

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