Lexus RX300 (MCU15). 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
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