ENGINE — 3UZ-FE ENGINE

703. Engine Control System Diagram

Vapor
Ignition Pressure
Fuel Pump Sensor
Resistor

Circuit Opening
Relay VSV
(for EVAP)
Fuel Pump
VSV
Intake Air Relay for Pressure
Temp. Sensor Switching
Valve
Mass VSV
Air Flow
Meter
Charcoal for Canister
Canister Closed Valve
Fuel Pump
Accelerator pedal
Throttle Position
position sensor
Sensor

Throttle VSV (for ACIS)

Control Motor
Injector Injector
Camshaft Timing Camshaft Timing
Oil Control Valve Oil Control Valve
Camshaft Position
VVT Sensor Sensor
*1 VVT Sensor
Ignition Coil Ignition Coil
(with Igniter) (with Igniter)

*2 *2

Knock Knock
Sensor Sensor

Crankshaft Position
*2
Sensor *2

ECM

Starter
Air
Conditioning Vehicle Speed Sensor
MIL (for Transmission)

Battery Park/Neutral Position Switch

DLC3

*1: Engine Coolant Temp. Sensor Electronic Controlled

*2: Heated Oxygen Sensor Transmission Solenoid
Valves
189EG08
 ENGINE — 3UZ-FE ENGINE

4. Layout of Main Components 71

Ignition Coil with Igniter

VVT Sensor
(Bank 1)
Heated Oxygen Sensor
VSV (for EVAP) Knock Sensor (Bank 2, Sensor 2) VSV
(Bank 2) (for
Throttle Control Fuel Pump Pressure
Motor Injector Switching
VVT Sensor Valve)
(Bank 2)
Mass Air
Flow Meter
VSV
(for Canister
Closed
Valve)

Vaper
Pressure
DLC 3 Sensor
Neutral Start Switch

Camshaft Heated Oxygen Sensor

Timing Oil (Bank 1, Sensor 2)
Control Valve
(Bank 2) Accelerator Pedal Position
Sensor
Engine Coolant
Temp. Sensor VSV for ACIS Heated Oxygen Sensor
(Bank 1, Sensor 1)
Throttle Position
Sensor Knock Sensor 189EG09
Crankshaft (Bank 1)
Position Camshaft
Sensor Position ECM
Heated Oxygen Sensor
Sensor (Bank 2, Sensor 1)

Camshaft
Timing Oil
Control Valve
(Bank 1)
 ENGINE — 3UZ-FE ENGINE

725. Main Components of Engine Control System

General

The following table compares the main components of the 3UZ-FE engine in the ’01 LS430 and 1UZ-FE
engine in the ’00 LS400.
Engine Type 3UZ-FE 1UZ-FE
Components Outline Quantity Outline Quantity
Mass Air Flow Meter Hot-Wire Type 1 
Crankshaft Position
Pick-Up Coil Type (36-2) 1 
Sensor (Rotor Teeth)
Camshaft Position Sensor
Pick-Up Coil Type (1) 1 
(Rotor Teeth)
VVT Sensor Pick-Up Coil Type (3) 2 
Throttle Position Sensor Linear Type 2 
Accelerator Pedal
Linear Type 2 
Position Sensor
Knock Sensor Built-In Piezoelectric Type 2 
Oxygen Sensor
(Bank 1, Sensor 1)
(Bank 2, Sensor 1) With Heater Type 4 
(Bank 1, Sensor 2)
(Bank 2, Sensor 2)
4-Hole Type with
Injector 8 
Air Assist

Mass Air Flow Meter

A hot-wire type mass air flow meter has been

adopted. This mass air flow meter, which is a plug-in
type, allows a portion of the intake air to flow through
the detection area. By directly measuring the mass
and the flow rate of the intake air, the detection preci- Intake Air
sion has been improved and the intake air resistance Temp. Sensor
has been reduced.

Hot-Wire 189EG10
 ENGINE — 3UZ-FE ENGINE

Crankshaft Position Sensor 73

The timing rotor of the crankshaft consists of 34 Timing Rotor

teeth, with 2 teeth missing. The crankshaft position
sensor outputs the crankshaft rotation signals every
10°, and the missing teeth are used to determine the
top-dead-center.

Crankshaft Position Sensor

Camshaft Position Sensor 151EG18

The camshaft position sensor is mounted on the left Timing Rotor

bank cylinder head. To detect the camshaft position,
a protrusion that is provided on the timing pulley is
used to generate 1 pulse for every 2 revolutions of
the crankshaft.

VVT Sensor Camshaft Position Sensor

151EG19

A VVT sensor is mounted on the intake side of each Timing Rotor

cylinder head. To detect the camshaft position, a tim- VVT Sensor
ing rotor that is provided on the intake camshaft is
used to generate 3 pulses for every 2 revolutions of
the crankshaft.

Intake Camshaft
151EG20
 ENGINE — 3UZ-FE ENGINE

746. VVT-i (Variable Valve Timing-intelligent) System

General

The VVT-i system is designed to control the intake camshaft within a wide range of 45° (of crankshaft
angle) to provide a valve timing that is optimally suited to the engine condition, thus realizing improved
torque in all the speed ranges and fuel economy, and reduce exhaust emissions.

VVT Sensors
Mass Air
Camshaft Timing Flow Meter
Oil Control Valves ECM
Throttle
Engine Coolant Position Sensor
Temp. Sensor

VVT-i
Controllers

Oil Pump

Crankshaft
Position Sensor 188EG47

ECM

Crankshaft Position Sensor Target Valve Timing Camshaft Timing

Oil Control Valves

Mass Air Flow Meter

Feedback
Duty Control
Throttle Position Sensor

Engine Coolant Temp. Sensor Correction

VVT Sensors Actual Valve Timing

157EG23
 ENGINE — 3UZ-FE ENGINE

Construction and Operation 75

1) VVT-i Controller

The VVT-i controller comprises the outer gear that is driven by the timing belt, the inner gear that is
affixed to the camshaft and a movable piston that is placed between the outer gear and inner gear. Having
helical splines (twisted, vertical grooves) on its inner and outer periphery, the piston moves in the axial
direction to shift the phase of the outer gear and inner gear, thus causing the valve timing to change continu-
ously.
The VVT tube drives the exhaust camshaft via the scissors gear that is installed on the back.

VVT-i Controller
VVT Tube

Piston
Intake Camshaft

Inner Gear

Exhaust Camshaft
Outer Gear

Scissors Gear
151EG29

2) Camshaft Timing Oil Control Valve

The camshaft timing oil control valve controls the

To VVT-i To VVT-i
spool valve position in accordance with the duty Controller Controller
control from the ECM thus allocating the hydraulic (Advance Side) (Retard Side)
pressure that is applied to the VVT-i controller to
the advance and the retard side. When the engine Coil
is stopped, the camshaft timing oil control valve Spring
is in the most retarded state.

Drain Drain Plunger

Spool
Spring Valve
Oil Pressure

165EG34
 ENGINE — 3UZ-FE ENGINE

76Operation

 The camshaft timing oil control valve selects the path to the VVT-i controller according to the advance,
retard or hold signal from the ECM. The VVT-i controller rotates the intake camshaft in the timing advance
or retard position or holds it according to the position where the oil pressure is applied.
Camshaft Timing Oil
Operation Control Valve Drive Signal
Description

Camshaft Timing
Piston Oil Control Valve When the camshaft timing oil
Advance Signal
control valve is positioned as il-
lustrated in accordance with the
Advance

advance signal from the ECM,

the oil pressure is applied to the
chamber at the advance side.
Then, the twist of the helical
Intake spline causes the camshaft to ro-
Camshaft Drain
Oil Pressure tate in the direction of timing ad-
Duty Ratio
Timing Pulley vance.
188EG48 157EG35

Retard Signal
When the camshaft timing oil
control valve is positioned as il-
lustrated in accordance with the
Retard

retard signal from the ECM, the

oil pressure is applied to the
chamber at the retard side. Then,
the twist of the helical spline
Drain causes the camshaft to rotate in
Oil Pressure
the direction of timing retard.
Duty Ratio
188EG49 157EG36

The ECM calculates the target

timing angle according to the trav-
Hold Signal
eling state to perform control as
described above. After setting at
the target timing, the valve timing
is held by keeping the camshaft
Hold

timing oil control valve in the neu-

tral position unless the traveling
state changes.
This adjusts the valve timing at
Duty Ratio
the desired target position and pre-
vents the engine oil from running
188EG50 157EG37 out when it is unnecessary.
 ENGINE — 3UZ-FE ENGINE

 In proportion to the engine speed, intake air volume, throttle position and water temperature, the ECM77
calculates an optimal valve timing under each driving condition and control the camshaft timing oil control
valve. In addition, ECM uses signal from the VVT sensors and the crankshaft position sensor to detect
the actual valve timing, thus performing feed back control to achieve the target valve timing.

Operation During Various Driving Condition (Conceptual Diagram) 

Full Load Performance

Range 4
Range 5

Engine Load
Range 3

Range 1, 2

150EG34
Engine Speed

Operation State Range Valve Timing Objective Effect

TDC
Latest Timing

Stabilized
Eliminating overlap to re- idling rpm
During Idling 1 EX IN duce blow back to the in-
take side Better fuel
economy

BDC 188EG51

To Retard Side

Ensured
Decreasing overlap to engine
At Light Load 2 EX IN eliminate blow back to the stability
intake side

188EG64

To Advance Side

Better fuel
Increasing overlap to economy
At Medium EX IN
3 increase internal EGR for Improved
load
pumping loss elimination emission
control
188EG65
 ENGINE — 3UZ-FE ENGINE

78 Operation State Range Valve Timing Objective Effect

TDC

Improved
In Low to Advancing the intake
torque in
Medium Speed EX IN valve close timing for vol-
4 low to
Range with umetric efficiency
medium
Heavy Load improvement
To Advance
speed range
Side
BDC 188EG66

Retarding the intake valve

In High Speed
EX IN close timing for volumetric Improved
Range with 5
efficiency output
Heavy Load
improvement
To Retard
Side
188EG67

Latest Timing

Eliminating overlap to pre-

vent blow back to the in- Stabilized
At Low take side leads to the lean fast idle rpm
— EX IN
Temperatures burning condition, and sta- Better fuel
bilizes the idling speed at economy
fast idling.
188EG52

Latest Timing

Upon Starting/ Eliminating overlap to

Improved
Stopping the — EX IN minimize blow back to the
startability
Engine intake side

188EG53
 ENGINE — 3UZ-FE ENGINE

7. ETCS-i (Electronic Throttle Control System-intelligent) 79

General

 The ETCS-i system, which realizes excellent throttle control in all the operating ranges, has been adopted.
However, in the new 3UZ-FE engine, the accelerator cable has been discontinued, and an accelerator posi-
tion sensor has been provided on the accelerator pedal. Accordingly, the limp-mode control during the fail-
safe mode has been changed.
 In the conventional throttle body, the throttle valve opening is determined invariably by the amount of the
accelerator pedal effort. In contrast, the ETCS-i uses the ECM to calculate the optimal throttle valve open-
ing that is appropriate for the respective driving condition and uses a throttle control motor to control the
opening.

 The ETCS-i controls the ISC (Idle Speed Control) system, the snow mode control system, the cruise con-
trol system, the TRAC (Traction Control) system, and the VSC (Vehicle Skid Control) system. In addition
to these controls, a function to control the adaptive laser cruise control has been added to the model with
the adaptive laser cruise control.
 The torque-activated power train control has been newly adopted. This control enables the engine to gener-
ate the necessary torque as desired by the driver, as well as to realize a smooth engine output characteristic.

Throttle Valve Throttle Position

Sensor
Accelerator Pedal
Position Sensor
Throttle
Control
Motor

Skid
Control
ECU

Mass Air Distance

ECM Control Laser Rador
Flow Meter Sensor*
ECU*

BEAN Passenger
Side Junction Snow Switch
Block ECU

Ignition Fuel
Coils Injectors

189EG11
*: with Adaptive Laser Cruise Control
 ENGINE — 3UZ-FE ENGINE

80Construction

Throttle Control Moter

Throttle Valve

Throttle Position
Sensor

Reduction
Gears Throttle Return Spring
188EG55

1) Accelerator Pedal Position Sensor

The accelerator pedal position sensor is attached to the accelerator pedal. This sensor converts the accelera-
tor pedal depressed angles into electric signals with two differing characteristics and outputs them to the
ECM. One is the VPA signal that linearly outputs the voltage along the entire range of the accelerator
pedal depressed angle. The other is the VPA2 signal that outputs an offset voltage.

V
5
Close
VPA2
Output Voltage

Open
VPA

EP2 VPA2 VCP2 EP1 VPA VCP1 0 Close Open

188EG56 188EG57
Accelerator Pedal Depressed Angle
 ENGINE — 3UZ-FE ENGINE

2) Throttle Position Sensor 81

The throttle position sensor is attached to the throttle body. This sensor converts the throttle valve opening
angles into electric signals with two differing characteristics and outputs them to the ECM. One is the
VTA signal that linearly outputs the voltage along the entire range of the throttle valve opening angle.
The other is the VTA2 signal that outputs an offset voltage.

V
Close
5

Output Voltage
Open VTA2

VTA

0 Close
E2 Open
VTA2 VTA VC
Throttle Valve Opening Angle
150EG40 150EG39

3) Throttle Control Motor

A DC motor with excellent response and minimal power consumption is used for the throttle control motor.
The ECM performs the duty ratio control of the direction and the amperage of the current that flows to
the throttle control motor in order to regulate the opening angle of the throttle valve.
 ENGINE — 3UZ-FE ENGINE

82Operation

The ECM drives the throttle control motor by determining the target throttle valve opening in accordance
with the respective operating condition.
In addition to the controls listed below, functions to effect torque-activated power train control and radar
cruise control (on models with adaptive laser cruise control) have been added.

1) Torque Activated Power Train Control  New Control

2) Nomal-mode Control, Power–mode control and Snow-mode Control
3) Idle Speed Control

4) Shift Shock Reduction Control

5) TRAC Throttle Control
6) VSC Coordination Control

7) Cruise Control
8) Adaptive Laser Cruise Control  New Control
1) Torque Activated Power Train Control

Controls the throttle to an optimal throttle valve opening that is appropriate for the driving condition such
as the amount of the accelerator pedal effort and the engine operating condition. As a result, excellent
throttle control and comfort in all operating ranges, as well as smooth startoff acceleration and elastic
acceleration have been achieved.

With Control
No Control
Vehicle’s
Longitudinal G

0
Time

Throttle Valve
Opening Angle

Accelerator
Pedal Depressed
Angle Constant Opening
0
188EG58
 ENGINE — 3UZ-FE ENGINE

2) Normal-mode Control, Power-mode control and Snow-mode Control 83

 Controls the throttle to an optimal throttle valve opening that is appropriate for the driving condition
such as the amount of the accelerator pedal effort and the engine operating condition in order to realize
excellent throttle control and comfort in all operating ranges.
 If turning ON the POWER switch of the pattern select switch and selecting the power-mode, the throttle
valve opening angle is controlled to react more directly to operation of the accelerator pedal than the
normal mode. With this, sporty driving is realized.

 In situations in which low-µ surface conditions can be anticipated, such as when driving in the snow,
the throttle valve can be controlled to help vehicle stability while driving over the slippery surface.
This is accomplished by turning on the SNOW switch of the pattern select switch, which, in response
to the amount of the accelerator pedal effort that is applied, reduces the engine output from that of
the normal driving level.

Power-mode

Throttle Valve Normal-mode

Opening Angle

Snow-mode

Accelerator Pedal
Opening Angle
189EG38

Conceptual Diagram

3) Idle Speed Control

Controls the ECM and the throttle valve in order to constantly effect ideal idle speed control.
4) Shift Shock Reduction Control

The throttle control is synchronized to the ECT (Electronically Controlled Transmission) control during
the shifting of the transmission in order to reduce the shift shock.
5) TRAC Throttle Control

As part of the TRAC system, the throttle valve is closed by a demand signal from the skid control ECU
if an excessive amount of slippage is created at a driving wheel, thus facilitating the vehicle in ensuring
stability and driving force.
6) VSC Coordination Control

In order to bring the effectiveness of the VSC system control into full play, the throttle valve opening
angle is controlled by effecting a coordination control with the skid control ECU.
7) Cruise Control

An ECM with an integrated cruise control ECU directly actuates the throttle valve to effect the operation
of the cruise control.
 ENGINE — 3UZ-FE ENGINE

84 8) Adaptive Laser Cruise Control

In addition to the functions provided by the conventional cruise control, the adaptive laser cruise control
uses a laser radar sensor and a distance control ECU to determine the distance of the vehicle driven ahead,
its direction, and relative speed. Thus, the system can effect deceleration cruising control, follow-up cruis-
ing control, cruising at a fixed speed control, and acceleration cruising control. To make these controls
possible, the ECM controls the throttle valve.

Fail-Safe

If an abnormal condition occurs with the ETCS-i system, the malfunction indicator lamp in the combination
meter illuminates to inform the driver.
The accelerator pedal position sensor comprises two sensor circuits. Therefore, if an abnormal condition
occurs in the accelerator pedal position sensor, and the ECM detects the abnormal voltage difference of
the signals between these two sensor circuits, the ECM transfers to the limp mode by limiting the accelerator
opening signal.
If an abnormal condition occurs in the throttle body system which comprises two sensor circuits, the ECM
detects the abnormal voltage difference of the signals between these two circuits and cuts off the current
to the throttle motor, causing the throttle valve to close. However, when the throttle motor is OFF, because
a return spring is provided in the throttle valve, the force of the spring keeps the throttle valve slightly
open from the fully closed state. In this state, fuel injection control and ignition timing retard control are
effected in accordance with the accelerator opening, thus enabling the vehicle to be operated within the
range of idling and limp mode.

Injectors ECM Ignition Coils

Accelerator Pedal Open

Position Sensor

Return
Throttle Spring Throttle
Position Throttle Control
Sensor Valve Motor

Accelerator Pedal Throttle Body 189EG43

Diagnosis

The diagnostic trouble codes can be output to a LEXUS hand-held tester via the DLC 3.
For details, refer to the 2001 LEXUS LS430 Repair Manual (Pub. No. RM812U).
 ENGINE — 3UZ-FE ENGINE

8. ACIS (Acoustic Control Induction System) 85

General

The ACIS (Acoustic Control Induction System) is realized by using a bulkhead to divide the intake manifold
into 2 stages, with an intake air control valve in the bulkhead being opened and closed to vary the effective
length of the intake manifold in accordance with the engine speed and throttle valve opening angle. This
increases the power output in all ranges from low to high speed.

System Diagram 

Throttle Position Sensor

Actuator

VSV
Intake Air Control
Valve Vacuum Tank

ECM

Crankshaft Position Sensor

151EG13
 ENGINE — 3UZ-FE ENGINE

86Construction

1) Intake Air Control Valve

The intake air control valve, which is provided in

Intake Air Front
the middle of the intake manifold in the intake air Control Valve
chamber, opens and closes to change the effective
length of the intake manifold in two stages.

188EG35
Actuator
2) VSV (Vacuum Switching Valve)

Controls the vacuum that is applied to the actuator by way of the signal (ACIS) that is output by the
ECM.

From Vacuum Tank

To Actuator

Atmosphere

151EG42

3) Vacuum Tank

Equipped with an internal check valve, the vacuum tank stores the vacuum that is applied to the actuator
in order to maintain the intake air control valve fully closed even during low-vacuum conditions.
 ENGINE — 3UZ-FE ENGINE

Operation 87

1) When the Intake Control Valve Closes (VSV ON)

The ECM activates the VSV to match the longer pulsation cycle so that the negative pressure acts on
the diaphragm chamber of the actuator. This closes the control valve. As a result, the effective length
of the intake manifold is lengthened and the intake efficiency in the low-to-medium speed range is improved
due to the dynamic effect of the intake air, thereby increasing the power output.

: Effective Intake Manifold Length

VSV ON

Throttle Valve Opening Angle

60°

151EG14
4700 (rpm)
Engine Speed
189EG22

2) When the Intake Control Valve Open (VSV OFF)

The ECM deactivates the VSV to match the shorter pulsation cycle so that atmospheric air is led into
the diaphragm chamber of the actuator and opens the control valve. When the control valve is open, the
effective length of the intake air chamber is shortened and peak intake efficiency is shifted to the high
engine speed range, thus providing greater output at high engine speeds.
88
: Effective Intake Manifold Length
VSV OFF

Throttle Valve Opening Angle

60°

4700 (rpm)
151EG15 Engine Speed

189EG23
 ENGINE — 3UZ-FE ENGINE

9. Cooling Fan System 89

General

A cooling fan system has been adopted by the 3UZ-FE engine on the ’01 LS430. To achieve an optimal
fan speed in accordance with the engine coolant temperature, vehicle speed, engine speed, and air condition-
ing operating conditions, the ECM calculates the proper fan speed and sends the signals to the cooling
fan ECU. Upon receiving the signals from the ECM, the cooling fan ECU actuates the fan motors.
Also, the fan speed is controlled by ECM using the stepless control.

Wiring Diagram 

Crankshaft
Position Sensor
Vehicle Speed Signal
(for Transmission)

Engine Coolant
Temp. Sensor BEAN
ECM
Air Condi- Center
tioning ECU Cluster Panel

Air Conditioning Switch

Air Conditioning
Pressure Sensor
Fan Main
Relay

Ignition Fan Motor No. 1

Cooling
Switch Fan ECU
Fan Motor No. 2

Ignition
Relay

Battery

189EG12
 ENGINE — 3UZ-FE ENGINE

90Operation

As illustrated below, the ECM determines the required fan speed by selecting the fastest fan speed from
among the following:
(A) The fan speed required by the engine coolant temperature, (B) the fan speed required by the air condition-
ing refrigerant pressure, (C) the fan speed required by the engine speed, and (D) the fan speed required
by the vehicle speed.

Fan Fan
Speed Speed

Engine Coolant Refrigerant

Temperature Pressure
(A) Fan speed required by (B) Fan speed required by air
engine coolant temperature conditioning refrigerant
189EG13 pressure 189EG14

Fan Fan
Speed Speed

Engine Vehicle
Speed Speed
(C) Fan speed required (D) Fan speed required
by engine speed by vehicle speed
189EG15 189EG16

10. Fuel Pump Control

A fuel cut control is adopted to stop the fuel pump when the airbag is deployed at the front or side collision.
In this system, the airbag deployment signal from the airbag sensor assembly is detected by the ECM, which
turns OFF the circuit opening relay.
After the fuel cut control has been activated, turning the ignition switch from OFF to ON cancels the fuel
cut control, thus engine can be restarted.

Front Airbag
Sensor
Assembly Circuit
Opening
Relay
Side and Curtain Airbag
Shield Airbag Sensor BEAN
Sensor Assembly
ECM
Assembly

Fuel Pump
Curtain Shield Resistor
Airbag Sensor Fuel Pump
Assembly Relay
Fuel Pump
Motor

189EG17