Lexus SC300 / Lexus SC400. Service manual — part 478

(c) Remove the two bolts and two nuts, disconnect the

throttle body from the air intake chamber.

(d) Disconnect the following hoses, and remove the throttle

body:

(1) PCV hose from throttle body
(2) Water by–pass hose from throttle body

(e) Remove the throttle body gasket.

(f) Remove the two water by–pass hoses and pipe

assembly.

FI–72

EFI SYSTEM – Air Induction System (Throttle Body)

INSPECTION OF THROTTLE BODY

1.

CLEAN THROTTLE BODY
(a) Using

a

soft brush and carburetor cleaner, clean the cast

parts.

(b) Using compressed air, clean all the passages and

apertures.

NOTICE: To prevent deterioration, do not clean the
throttle position sensor and DP.

2. INSPECT

THROTTLE VALVE AND THROTTLE POSI TION

SENSOR

A. Inspect throttle valve

Check that there is no clearance between the throttle stop
screw and throttle lever when the throttle valve is fully closed.

B. Inspect throttle position sensor

(a) Insert a 40 mm (0.016 in.) or 0.65 mm (0.026 in.) feeler

gauge between the throttle stop screw and stop lever.

(b) Using an ohmmeter, measure the resistance between

each terminal.

Clearance between

Clearance between

lever and stop screw

Between terminals

Resistance

lever and stop screw

Between terminals

Resistance

0 mm (0 in.)

VTA1–E2

0.2–0.8

0.40 mm (0.016 in.)

IDL1–E2

2.3 k

or less

0.65 mm (0.026 in.)

IDL1–E2

Infinity

Throttle valve fully
open

VTA1–E2

3.3–10.0 k

–

VC–E2

4.0–9.0 k

C. If necessary, adjust throttle position sensor

(a) Loosen the two set screws of the sensor.

FI–73

EFI SYSTEM – Air Induction System (Throttle Body)

(b) Insert a 0.40 mm (0.016 in.) feeler gauge, between the

throttle stop screw and stop lever.

(c) Connect the test probe of an ohmmeter to the terminals

IDL1 and E2 of the sensor.

(d) Gradually turn the sensor clockwise until the ohmmeter

deflects, and secure it with the two set screws.

(e) Recheck the continuity between terminals IDL1 and E2.

Clearance between

lever and stop screw

Continuity (IDL1–E2)

0.40 mm (0.016 in.)

Continuity

0.65 mm (0.026 in.)

No continuity

3. (w/

TRAC)

INSPECT SUB–THROTTLE ACTUATOR, SUBTHROTTLE
VALVE AND SUB–THROTTLE POSITION SENSOR

A.

Inspect sub–throttle actuator
Using an ohmmeter, measure the resistance between the ter-
minals (ACM–A and Å, BCM–B and B).

Resistance: 0.5–1.0

If the resistance is not as specified, replace the actuator
valve.

B. Inspect sub–throttle actuator

Remove the three screws and sub–throttle actuator.

FI–74

EFI SYSTEM – Air Induction System (Throttle Body)

C. Inspect

sub–throttle

valve

Check that there is no clearance between the throttle stop
screw and throttle valve gear when the sub–throttle valve is
fully closed.

D. Inspect sub–throttle position sensor

(a) Insert

a

0.30 mm (0.012 in.) or 0.50 mm (0.020 in.) feeler

gauge between the throttle stop screw and throttle valve
gear.

(b) Using an ohmmeter, measure the resistance between

each terminal.

Clearance between

lever and stop screw

Between terminals

Resistance

0 mm (0 in.)

VTA2–E2

0.2–0.8

0.30 mm (0.012 in.)

IDL2–E2

2.3 k

or less

0.50 mm (0.020 in.)

IDL2–E2

Infinity

Throttle valve fully
open

VTA2–E2

3.3–10.0 k

–

VC–E2

4.0–9.0 k

E.

If necessary, adjust sub–throttle position sensor
(a) Loosen the two set screws of the sensor.

(b) Insert a 0.30 mm (0.012 in.) feeler gauge, between the

throttle stop screw and throttle valve gear.

(c) Connect the test probe of an ohmmeter to the terminals

IDL2 and E2 of the sensor.

FI–75

EFI SYSTEM – Air Induction System (Throttle Body)