Lexus ES300 (1997 year). Service manual — part 333

P01559

Throttle Valve

From

Air

Cleaner

Signal

ECM

Valve

IAC Valve

To Cylinders

Intake Air Chamber

S06462

From

Instrument Panel J/B

3

IGN

Ignition Switch

MAIN

From Battery

B–G

FL

7

1K

1W

B–R

F6

F8

1

1

Fusible

Link
Block

B

1

7

2

4

EFI

Engine Room J/B

EFI Relay

1

2

3

5

2A

2K

2J

2F

B–Y

W–B

EC

Junction

J23

IAC Valve

Connector

Junction

B

J28

B

J29

B–Y

B–Y

9 IK3

B–Y

R–W

Y–B

2

1

3

Connector

E10

E10

23

22

ECM

RSO

E01

RSC

E01

A

A

–

DIAGNOSTICS

ENGINE

DI–109

261

1997 LEXUS ES300 (RM511U)

DTC

P0505

Idle Control System Malfunction

CIRCUIT DESCRIPTION

The rotary solenoid type IAC valve is located in front of the in-
take air chamber and intake air bypassing the throttle valve is
directed to the IAC valve through a passage.
In this way the intake air volume bypassing the throttle valve is
regulated, controlling the engine speed.
The ECM operates only the IAC valve to perform idle–up and
provide feedback for the target idling speed.

DTC No.

DTC Detecting Condition

Trouble Area

P0505

Idle speed continues to vary greatly from the target speed

(2 trip detection logic)

IAC valve is stuck or closed

Open or short in IAC valve circuit

Open or short in A/C signal circuit

Air intake (hose loose)

WIRING DIAGRAM

DI09Z–01

A00236

RSO(+)

RSC(+)

E10 Connector

BE6653
P23877

ON

DI–110

–

DIAGNOSTICS

ENGINE

262

1997 LEXUS ES300 (RM511U)

INSPECTION PROCEDURE

1

Check air induction system (See page

SF–63

).

NG

Repair or replace.

OK

2

Check A/C signal circuit (See page

DI–569

).

NG

Repair or replace.

OK

3

Check voltage terminals RSO, RSC of ECM connector and body ground.

PREPARATION:
(a)

Remove the glove compartment (See page

SF–65

).

(b)

Disconnect the E10 connector of ECM.

(c)

Turn ignition switch ON.

CHECK:
Measure voltage between terminals RSO, RSC of ECM con-
nector and body ground.
OK:

Voltage: 9

∼

14 V

OK

Go to step 5.

NG

–

DIAGNOSTICS

ENGINE

DI–111

263

1997 LEXUS ES300 (RM511U)

4

Check IAC valve (See page

SF–36

).

NG

Replace IAC valve.

OK

Check for open and short in harness and

connector between engine room J/B and IAC valve, IAC

valve and ECM (See page

IN–27

).

5

Check operation of IAC valve (See page

SF–40

).

NG

Repair or replace IAC valve.

OK

Check and replace ECM (See page

IN–27

).

S00251

From Battery

Ignition Coil

Spark Plug

IGC1

IGC2

IGC3

GND

TAC

IGT1

IGT2

IGT3

IGF

To Tachometer

ECM

G

NE

Camshaft

Position

Sensor

Crankshaft

Position

Sensor

Various

Sensor

No.2 Cylinder

No.1 Cylinder

No.4 Cylinder

No.3 Cylinder

No.6 Cylinder

No.5 Cylinder

DI–112

–

DIAGNOSTICS

ENGINE

264

1997 LEXUS ES300 (RM511U)

DTC

P1300

Igniter Circuit Malfunction

CIRCUIT DESCRIPTION

A DIS (Direct Ignition System) has been adopted. The DIS improves the ignition timing accuracy, reduces
high–voltage loss, and enhances the overall reliability of the ignition system by eliminating the distributor.
The DIS is a 2–cylinder simultaneous ignition system which ignites 2 cylinders simultaneously with one igni-
tion coil. In the 2–cylinder simultaneous ignition system, each of the 2 spark plugs is connected to the end
of the secondary winding. High voltage generated in the secondary winding is applied directly to the spark
plugs. The sparks of the 2 spark plugs pass simultaneously from the center electrode to the ground elec-
trode.
The ECM determines ignition timing and outputs the ignition signals (IGT) for each cylinder. Based on IGT
signals, the igniter controls the primary ignition signals (IGC) for all ignition coils. At the same time, the igniter
also sends an ignition confirmation signal (IGF) as a fail–safe measure to the ECM.

DTC No.

DTC Detecting Condition

Trouble Area

P1300

Condition (a) is repeated 3 times consecutively during 6

consecutively IGT signals while engine is running

(a) IGF signal is not input to ECM for 2 or more ignitions

Open or short in IGF or IGT circuit from igniter to ECM

Igniter

ECM

DI0A0–01