Lexus RX300 (MCU15). Manual - part 317

I07347

Instrument Panel J/B

ECU–IG

I16977

ON

GND

(–)

(+)

B

DI–500

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Check ECU–IG fuse.

PREPARATION:
Remove the ECU–IG fuse from driver side junction block.
CHECK:
Check continuity of ECU–IG fuse.
OK:

Continuity

NG

Check for short in all the harness and compo-
nents connected to ECU–IG fuse.

OK

2

Check voltage between terminals B and GND of cruise control ECU connector.

PREPARATION:
(a)

Remove the ECU with connector still connected.

(b)

Turn ignition switch ON.

CHECK:
Measure voltage between terminals B and GND of ECU con-
nector.
OK:

Voltage: 10 – 14 V

OK

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

I16978

GND

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–501

LEXUS RX300   (RM785E)

NG

3

Check resistance between terminal GND of cruise control ECU connector and
body ground.

CHECK:
Measure resistance between terminal GND of ECU connector
and body ground.
OK:

Resistance: Below 1 Ω

NG

Repair or replace harness or connector.

OK

Check and repair harness and connector be-
tween cruise control ECU and battery (See
page IN–32).

I19252

Cruise Control ECU

C16

5

11

4

CCS

ECC

RES/ACC

CRUISE

CANCEL

C13
Cruise Control Switch

BR

BR

SET/COAST

A

IE

L

CCS

J5
J/C

DI–502

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

LEXUS RX300   (RM785E)

Control Switch Circuit (Cruise Control Switch)

CIRCUIT DESCRIPTION

This circuit carries the SET/COAST, RESUME/ACCEL and CANCEL signals (each voltage) to the ECU.

WIRING DIAGRAM

DI08R–23

Input Signal

Indicator Light
 Blinking Pattern

SET/COAST
switch

RESUME/ACCEL
switch

CANCEL switch

2 Pulses

ON

OFF

ON

OFF

3 Pulses

ON

OFF

SW OFF

SW ON

I16970

ON

CCS

(–)

(+)

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–503

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE

1

Input signal check.

PREPARATION:
See input signal check on page DI–474.
CHECK:
Check the indicator light operation when each of the SET/
COAST, RESUME/ACCEL and CANCEL is turned on.
OK:

SET/COAST, RESUME/ACCEL switch
The signals shown in the table on the left should be
output when each switch is ON. The signal should
disappear when the switch is turned OFF.
CANCEL switch
The indicator light goes off when the cancel switch is
turned ON.

OK

Wait and see.

NG

2

Check voltage between terminals CCS of cruise control ECU connector and body
ground.

PREPARATION:
(a)

Remove the ECU with connector still connected.

(b)

Turn ignition switch ON.

CHECK:
Measure voltage between terminals 18 of ECU connector and
body ground, when each of the SET/COAST, RESUME/AC-
CEL and CANCEL  is turned ON.

Switch position

Resistance (V)

Neutral

10 – 16 V

MAIN

Below 0.5 V

RES/ACC

2.0 – 4.6 V

SET/COAST

4.0 – 7.9 V

CANCEL

6.0 – 11.0 V

NG

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

OK