Lexus RX300 (MCU15). Service manual - part 311

N17520

N17520

N17520

DI–476

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DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

4.

PROBLEM SYMPTOM CHECK (ROAD TEST)

(a)

Inspect the SET switch.
(1)

Push the main switch ON.

(2)

Drive at a desired speed (40 km/h (25 mph) or high-
er).

(3)

Press the control switch to the SET/COAST.

(4)

After releasing the switch, check that the vehicle
cruises at the desired speed.

(b)

Inspect the ACCEL switch.
(1)

Push the main switch ON.

(2)

Drive at a desired speed (40 km/h (25 mph) or high-
er).

(3)

Check that the vehicle speed increases while the
control switch is turned to RES/ACC, and that the
vehicle cruises at the set speed when the switch is
released.

(4)

Momentarily raise the control switch upward to the
RES/ACC position and then immediately release it.
Check that the vehicle speed increases by approx.
1.5 km/h (Tap–up  function).

(c)

Inspect the COAST switch.
(1)

Push the main switch ON.

(2)

Drive at a desired speed (40 km/h (25 mph) or high-
er).

(3)

Check that the vehicle speed decreases while the
control switch is turned to SET/COAST, and the ve-
hicle cruises at the set speed when the switch is re-
leased.

(4)

Momentarily pull the control switch down to SET/
COAST, and then immediately release it. Check
that the vehicle speed decreases by about 1.5 km/h
(Tap–down function).

N17520

N17520

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DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–477

LEXUS RX300   (RM785E)

(d)

Inspect the CANCEL switch.
(1)

Push the main switch ON.

(2)

Drive at a desired speed (40 km/h (25 mph) or high-
er).

(3)

When operating one of the following operations,
check that the cruise control system is cancelled
and that the normal driving mode is reset.

S

Depress the brake pedal

S

Shift to except D position

S

Push the main switch OFF

S

Pull the cruise control switch to CANCEL

(e)

Inspect the RESUME switch.
(1)

Push the main switch ON.

(2)

Drive at a desired speed (40 km/h (25 mph) or high-
er).

(3)

When operating one of the following operations
check that the cruise control system is cancelled
and that the normal driving mode is reset.

S

Depress the brake pedal

S

Shift to except D position

S

Push the main switch OFF

S

Pull the cruise control switch to CANCEL

(4)

After the control switch is turned to RES/ACC at the
driving speed of more than 40 km/h (25 mph), check
that the vehicle restores the speed prior to the can-
cellation.

N17520

(1)

(2)

(1)

No.

Operation Method

CRUISE MAIN Indicator Light
Blinking Pattern

Diagnosis

1

Turn SET/COAST switch ON

2

Turn RES/ACC switch ON

3

Turn CANCEL switch ON

Turn stop light switch ON
Depress brake pedal

Turn PNP switch OFF
(Shift to except D position)

4

Drive at about 40 km/h 
(25 mph)or higher

Drive at about 40 km/h
(25 mph) or below

Light

ON

OFF

Light

ON

OFF

Light

ON

OFF

Switch ON

Switch OFF

Light

ON

OFF

Switch OFF

Switch ON

SET/COAST switch circuit
is normal

RES/ACC switch circuit
is normal

CANCEL switch circuit
is normal

Stop light switch circuit
is normal

PNP switch circuit is
normal

Vehicle Speed Sensor is
normal

Light

ON

OFF

Light

ON

OFF

1sec.

0.25 sec.

0.25 sec.

DI–478

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DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

5.

INPUT SIGNAL CHECK

HINT:
(1) For check No.1 ∼ No.3:
Turn ignition switch ON.
(2) For check No.4:

S

Jack up the vehicle.

S

Start the engine.

S

Shift to D position.

(a)

Pull the control switch to SET/COAST or RES/ACC posi-
tion and hold it down or up (1).

(b)

Push the main switch ON (2).

(c)

Check that the CRUISE MAIN indicator light blinks twice
or 3 times repeatedly after 3 seconds.

(d)

Turn the SET/COAST or RES/ACC switch OFF.

(e)

Operate each switch as listed in the table below.

(f)

Read the blinking pattern of the CRUISE MAIN indicator
light.

(g)

After performing the check, turn the main switch OFF.

HINT:
When 2 or more signals are input to the ECU, the lowest num-
bered code will be displayed 1st.

DI08I–13

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DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–479

LEXUS RX300   (RM785E)

DIAGNOSTIC TROUBLE CODE CHART

If a malfunction code is displayed during the DTC check, check the circuit listed for that code in the table
below and proceed to the appropriate page.

DTC No.

(See Page)

Circuit Inspection

Trouble Area

11, 15

(DI–484)

Actuator Motor Circuit

S

Actuator motor

S

Harness or connector between cruise control ECU and

actuator motor

S

Cruise control  ECU

12

(DI–486)

Actuator Magnetic Clutch Circuit

S

STOP Fuse

S

Stop light switch

S

Actuator magnetic clutch

S

Harness or connector between cruise control ECU and

actuator magnetic clutch, actuator magnetic clutch and body

ground

S

Cruise control  ECU

14

(DI–490)

Actuator Mechanical Malfunction

S

Actuator motor (actuator lock: motor, arm)

S

Cruise control  ECU

21

(DI–492)

Open in Vehicle Speed Sensor Circuit

S

Combination meter

S

Harness or connector between cruise control ECU and com-

bination meter, combination meter and vehicle speed sensor

S

Vehicle speed sensor

S

Cruise control  ECU

23

(DI–495)

Vehicle Speed Signal Abnormal

S

Vehicle speed sensor

S

Cruise control  ECU

41

Cruise control ECU

S

Cruise control  ECU

42

Source voltage drop

S

Power source

51

(DI–496)

Idle Signal Circuit

S

Throttle position sensor

S

Harness or connector between Engine and ECT ECU and

throttle position sensor

S

Harness or connector between cruise control ECU and ECM

S

Cruise control  ECU