Toyota Sequoia (2005). Manual - part 981

80

SEQUOIA (EM00Z0U)

Engine Control

The engine control system utilizes a microcomputer and maintains overall control of the engine, transmission etc. An outline
of the engine control is given here.

1. Input Signals

(1) Engine coolant temp. signal circuit

The engine coolant temp. sensor detects the engine coolant temp. and has a built–in thermistor with a resistance which
varies according to the engine coolant temp. The engine coolant temp. is input into TERMINAL THW of the engine
control module as a control signal.

(2) Intake air temp. signal circuit

The intake air temp. sensor is installed in the mass air flow meter and detects the intake air temp., which is input as a
control signal to TERMINAL THA of the engine control module.

(3) Oxygen sensor signal circuit

The oxygen density in the exhaust emission is detected and is input as a control signal from the heated oxygen sensors
to TERMINALS OX1B, OX2B of the engine control module.

(4) RPM signal circuit

The camshaft position is detected by the camshaft position sensor and is input into TERMINAL G2+ of the engine
control module as a control signal. Also, the engine RPM is detected by the crankshaft position sensor and the signal is
input into TERMINAL NE+ of the engine control module.

(5) Throttle position sensor signal circuit

The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINALS
VTA1, VTA2 of the engine control module.

(6) Vehicle speed circuit

The vehicle speed sensor (Combination meter) detects the vehicle speed, and the signal is input into TERMINAL SPD
of the engine control module via the combination meter.

(7) Battery signal circuit

Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition SW is turned on, the
voltage for engine control module start up power supply is applied through the EFI relay, to TERMINALS +B, +B2 of the
engine control module. The current from the IGN1 fuse flows to TERMINAL IGSW of the engine control module, and
voltage is constantly applied to TERMINAL +BM.

(8) Intake air volume signal circuit

The intake air volume is detected by the mass air flow meter, and is input as a control signal to TERMINAL VG of the
engine control module.

(9) Stop light SW signal circuit

The stop light SW is used to detect whether the vehicle is braking or not, and the signal is input into TERMINAL STP of
the engine control module as a control signal.

(10) Starter signal circuit

To confirm whether the engine is cranking, the voltage applied to the starter motor when the engine is cranking is
detected, and is input into TERMINAL STA of the engine control module as a control signal.

(11) Engine knock signal circuit

Engine knocking is detected by the knock sensors, and is input into TERMINALS KNK1, KNK2 of the engine control
module as a control signal.

(12) A/C SW signal system

The operating voltage of the A/C magnetic clutch is detected and input in the form of a control signal to TERMINAL AC1
of the engine control module.

(13) Air fuel ratio signal system

The air fuel ratio is detected by air fuel ratio sensor and input as a control signal into TERMINALS A1A+, A2A+ of engine
control module.

System Outline

SEQUOIA (EM00Z0U)

81

2. Control System

∗

SFI system
The SFI system monitors the engine condition through the signals input from each sensors to the engine control module.
The control signal is sent to the engine control module TERMINALS #10, #20, #30, #40, #50, #60, #70 and #80 to operate
the injector (Fuel injection). The SFI system controls the fuel injection by the engine control module in response to the
driving conditions.

∗

ESA system
The ESA system monitors the engine condition through the signals input from each sensors to the engine control module.
The best ignition timing is decided according to this data and the data memorized in the engine control module. The
control signal is output to TERMINALS IGT1, IGT2, IGT3, IGT4, IGT5, IGT6, IGT7, IGT8, and these signals control the
igniter to provide the best ignition timing.

∗

Heated oxygen sensor heater control system
The heated oxygen sensor heater control system turns the heater on when the intake air volume is low (Temp. of exhaust
emission is low), and warms up the heated oxygen sensors to improve their detection performance. The engine control
module evaluates the signals from each sensors, and outputs current to TERMINALS HT1B or HT2B to control the heater.

∗

Air fuel ratio sensor heater control system
The air fuel ratio sensor heater control system turns the heater on when the intake air volume is low (Temp. of exhaust
emission is low), and warms up the air fuel ratio sensor to improve detection performance of the sensor.
The engine control module evaluates the signals from each sensor, current is output to TERMINALS HA1A and HA2A,
controlling the heater.

∗

Fuel pump control system
The engine control module supplies current to TERMINAL FPR, and controls the operation speed of the fuel pump with
the FUEL PUMP relay.

∗

ACIS
The ACIS includes a valve in the bulkhead separating the surge tank into two parts. This valve is opened and closed in
accordance with the driving conditions to control the intake manifold length in two stages, for increased engine output in all
ranges from low to high speeds.

∗

ETCS–i
The ETCS–i controls the engine output at its optimal level in accordance with the opening of the accelerator pedal, under
all driving conditions.

∗

Engine start control system
The engine control module allows power to be supplied from the TERMINAL STAR/NSW to the STA relay via park/neutral
position SW until complete combustion is confirmed by engine RPM after the detection of ignition SW ST signal by the
TERMINAL STSW.
With this arrangement, engine can be started without holding the ignition key in the ST position. At the same time, the
TERMINAL ACCR is controlled so that the engine control module turns off ACC CUT relay, shutting off power to the
accessories.

∗

VVT–i
Controls the intake camshaft to an optimal valve timing in accordance with the engine condition.

∗

Air Injection System
It is the system to improve exhaust control performance by activating catalyst at early stage, which is realized when air is
pressed and sent into the exhaust pipe forcibly by the air injection pump at starting engine in cold condition.

3. Diagnosis System

When there is a malfunction in the engine control module signal system, the malfunctioning system is recorded in the
memory. The malfunctioning system can be found by reading the code displayed on the malfunction indicator lamp.

4. Fail–Safe System

When a malfunction has occurred in any system, there is a possibility of causing engine trouble due to continued control
based on that system. In that case, the fail–safe system either controls the system using the data (Standard values)
recorded in the engine control module memory, or else stops the engine.

82

SEQUOIA (EM00Z0U)

Engine Control

  :  Parts Location

Code

See Page

Code

See Page

Code

See Page

A10

40

I1

41

J45

B

44

A20

42

I2

41

J48

A

44

A37

42

I3

41

J49

B

44

A38

40

I4

41

J51

A

44

A39

40

I5

41

J52

B

44

A40

A

40

I6

41

J53

A

44

A41

B

40

I7

41

J54

B

44

A42

40

I8

41

J55

C

44

A43

40

I9

41

J56

D

44

A46

40

I10

41

K1

41

C1

40

I11

41

K2

41

C2

40

I12

41

L5

47

C5

A

42

I13

41

M1

41

C6

B

42

I14

41

P1

41

C13

40

I15

41

S1

41

C14

40

I16

41

S14

45

D6

43

I22

43

S25

45

E2

40

J2

41

T5

45

E4

A

43

J3

41

T14

41

E5

B

43

J5

41

T16

45

E6

C

43

J8

44

V1

41

E7

D

43

J14

A

44

V4

41

E8

E

43

J15

B

44

V12

41

F9

40

J16

44

V14

41

F10

22, 40

J17

44

V15

41

F19

46

J18

44

V16

41

F23

43

J42

44

V17

41

H2

40

J43

44

H4

40

J44

A

44

: Relay Blocks

Code

See Page

Relay Blocks (Relay Block Location)

2

26

Engine Room R/B No.2 (Engine Compartment Left)

SEQUOIA (EM00Z0U)

83

: Junction Block and Wire Harness Connector

Code

See Page

Junction Block and Wire Harness (Connector Location)

1A

33

Cowl Wire and Instrument Panel J/B (Lower Finish Panel)

1D

33

Cowl Wire and Instrument Panel J/B (Lower Finish Panel)

1E

33

Cowl Wire and Instrument Panel J/B (Lower Finish Panel)

1F

33

Cowl Wire and Instrument Panel J/B (Lower Finish Panel)

1H

1J

33

Engine Room Main Wire and Instrument Panel J/B (Lower Finish Panel)

1L

33

Engine Room Main Wire and Instrument Panel J/B (Lower Finish Panel)

2A

29

Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)

2B

29

Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)

2C

29

Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)

2F

29

Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)

2G

2H

3A

36

Cowl Wire and Sub J/B No.3 (Upper the Accelerator Pedal)

3B

36

Cowl Wire and Sub J/B No.3 (Upper the Accelerator Pedal)

4A

38

Cowl Wire and Sub J/B No.4 (Upper the Accelerator Pedal)

4B

38

Cowl Wire and Sub J/B No.4 (Upper the Accelerator Pedal)

4D

38

Cowl Wire and Sub J/B No.4 (Upper the Accelerator Pedal)

4E

: Connector Joining Wire Harness and Wire Harness

Code

See Page

Joining Wire Harness and Wire Harness (Connector Location)

EB4

50

Engine No.2 Wire and Engine Wire (Near the Starter)

EB5

50

Engine No.2 Wire and Engine Wire (Near the Starter)

EC1

50

Engine No.2 Wire and Differential Wire (Near the Transmission)

ED2

50

Engine No.2 Wire and Engine Room Main Wire (Under the Engine Room J/B)

IA1

51

Engine Room Main Wire and Cowl Wire (Cowl Side Panel LH)

IA4

51

Engine Room Main Wire and Cowl Wire (Cowl Side Panel LH)

IA5

51

Engine Room Main Wire and Cowl Wire (Cowl Side Panel LH)

IG4

51

Engine Wire and Cowl Wire (Right Side of Instrument Panel)

IJ3

51

Floor No.1 Wire and Cowl Wire (Right Kick Panel)

IL2

51

Engine Room Main Wire and Cowl Wire (Cowl Side Panel RH)

BB1

52

Frame Wire and Floor No.1 Wire (Under the Front Passenger’s Seat)

BB2

52

Frame Wire and Floor No.1 Wire (Under the Front Passenger’s Seat)

BN1

52

Frame No.2 Wire and Frame Wire (Left Side of No.6 Crossmember)

: Ground Points

Code

See Page

Ground Points Location

EB

50

Rear Left Side of Cylinder Head

EC

50

Front Left Side of Cylinder Head

ED

50

Front Fender Apron LH

EN

50

Left Side of Cylinder Block

IE

51

Cowl Side Panel LH

IG

51

Cowl Side Panel RH

BI

52

Rear Side No.4 Crossmember of Side Rail LH

BK

52

Center Pillar RH