Lexus RX300 (MCU15). Service manual - part 319

Input Signal

Indicator Light 
Blinking Pattern

Turn PNP switch
OFF (Shift to posi-
tions except D )

Light

ON

OFF

SW ON

SW OFF

DI–508

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check starter operation.

CHECK:
Check that the starter operates normally and that the engine starts.

NG

Replace starter.

OK

2

Input signal check.

PREPARATION:
See input signal check on page DI–474.
CHECK:
Check the indicator light when shifting into positions except D.
OK:

The indicator light goes off when shifting into posi-
tions except D.

OK

Proceed to next circuit inspection shown in
problem symptom table (See page DI–483).

NG

I16975

ON

D

(–)

(+)

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–509

LEXUS RX300   (RM785E)

3

Check voltage between terminal D of cruise control ECU connector and body
ground.

PREPARATION:
Turn ignition switch ON.
CHECK:
Measure voltage between terminal D of  ECU connector and
body ground when shifting into D range and other positions.
OK:

Shift Position

Voltage

D position

10 – 14 V

Other positions

Below 1 V

OK

Proceed to next circuit inspection shown in
problem symptom table (See page DI–483).

NG

4

Check harness and connector between cruise control ECU and neutral start
switch (See page IN–32).

NG

Repair or replace harness or connector.

OK

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

Input Signal

Indicator Light
Blinking Pattern

Clutch switch 
OFF (Depress
clutch pedal)

Light

ON

OFF

SW ON

SW OFF

DI–510

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

Clutch Switch Circuit

CIRCUIT DESCRIPTION

When the clutch pedal is depressed, the clutch switch sends a signal to the cruise control ECU. When the
signal is input to the cruise control ECU during cruise control driving, the cruise control ECU cancels cruise
control.

WIRING DIAGRAM

Refer to neutral start switch circuit on page DI–507.

INSPECTION PROCEDURE

1

Check starter operation.

CHECK:
Check that the starter operates normally and that the engine starts.

NG

Proceed to engine troubleshooting.

OK

2

Input signal check.

PREPARATION:
See input signal check on page DI–474.
CHECK:
Check the indicator lights when clutch pedal is depressed.
OK:

The indicator light goes off when shifting into clutch
pedal is depressed.

OK

Proceed to next circuit inspection shown in
problem symptom table (See page DI–483).

NG

DI08W–08

I16976

ON

D

(–)

(+)

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–511

LEXUS RX300   (RM785E)

3

Check voltage between terminal D of cruise control ECU and body ground.

PREPARATION:
Turn ignition switch ON.
CHECK:
Measure voltage between terminal D of cruise control ECU con-
nector and body ground when clutch pedal is depressed and
pushed in.
OK:

Shift Position

Voltage

Clutch pedal depressed

10 – 14 V

Clutch pedal pushed in

Below 1 V

OK

Proceed to next circuit inspection shown in
problem symptom table (See page DI–483).

NG

4

Check for open in harness and connector between ECU and GAUGE fuse (See
page IN–32).

NG

Repair or replace harness or connector.

OK

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