Lexus RX300 (MCU15). Service manual - part 313

DI08M–21

Duty Ratio =

A + B

A

x 100 (%)

ON

OFF

A

B

1 cycle

I19249

C5 
Cruise Control Actuator

Cruise Control 
ECU

II1

II1

MC

MO

L–B

2

1

L–R

L–B

9

10

7

15

C16

C16 MO

MC

L–R

DI–484

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

CIRCUIT INSPECTION

DTC

11, 15

Actuator Motor Circuit

CIRCUIT DESCRIPTION

The actuator motor is operated by signals from the ECU. Acceleration and deceleration signals are trans-
mitted according to changes in the Duty Ratio (See below).
Duty Ratio
The duty ratio is the ratio of the period of continuity in one cycle. For example, if A is the period of continuity
in one cycle, and B is the period of non–continuity.

DTC No.

Detection Item

Trouble Area

11

Short in actuator motor circuit.

S

Actuator motor

S

Harness or connector between cruise control ECU and

actuator motor

S

Cruise control ECU

15

Open in actuator motor circuit.

S

Actuator motor

WIRING DIAGRAM

I00004

I00151

2

1

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–485

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check resistance between terminals MO and MC of actuator motor.

PREPARATION:
(a)

Turn ignition switch OFF.

(b)

Disconnect the actuator connector.

CHECK:
Measure resistance between terminals 1 and 2.
HINT:
If control plate is in fully opened or fully closed positions, resis-
tance can not be measured.
OK:

Resistance: more than 4.2 Ω

NG

Replace cruise control actuator.

OK

2

Check for open and short in harness and connectors between cruise control
ECU and actuator motor (See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace cruise control ECU.
(See page IN–32).

DI–486

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

DTC

12

Actuator Magnetic Clutch Circuit

CIRCUIT DESCRIPTION

This circuit turns on the magnetic clutch inside the actuator during cruise control operation according to the
signal from the ECU. If a malfunction occurs in the actuator or speed sensor, etc. during cruise control opera-
tion, the rotor shaft between the motor and control plate is released.
When the brake pedal is depressed, the stop light switch turns on, supplying electrical power to the stop light.
Power supply to the magnetic clutch is mechanically cut and the magnetic clutch is turned OFF.
When driving downhill, if the vehicle speed exceeds the set speed by 8 km/h (5 mph), the ECU turns the
safety magnet clutch OFF. If the vehicle speed later drops to within 5 km/h (3 mph), cruise control at the set
speed is resumed.

DTC No.

Detection Item

Trouble Area

12

Short in actuator magnetic clutch circuit.

Open (0.8 sec.) in actuator magnetic clutch circuit.

S

STOP Fuse

S

Stop light switch

S

Actuator magnetic clutch

S

Harness or connector between cruise control ECU and actua-

tor magnetic clutch, actuator magnetic clutch and body

ground

S

Cruise control ECU

DI7IR–02

I21176

Cruise Control ECU

2

1

3

4

3

to STOP Fuse

8

S10
Stop Light Switch

4

C5
Cruise Control Actuator
D

 Actuator Magnetic Clutch

II1

BR

J/B No.5

5E

5B

3

L

STP

C16

C16

G–W

G–B

L–Y

11

13

IE

L–W

16

L–W

G–W

BR

II1

18

J5
J/C

A

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–487

LEXUS RX300   (RM785E)

WIRING DIAGRAM