Lexus ES300 (1997 year). Manual — part 432

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–505

657

1997 LEXUS ES300 (RM511U)

Stop Light Switch Circuit

CIRCUIT DESCRIPTION

When the brake pedal is depressed, the stop light switch sends a signal to the ECU. When the ECU receives
this signal, it cancels the cruise control.
A fail–safe function is provided so that the cancel functions normally, even if there is a malfunction in the stop
light signal circuit.
The cancel conditions are: Battery positive voltage at terminal STP–
When the brake is on, battery positive voltage normally applies through the STOP fuse and stop light switch
to terminal STP– of the ECU, and the ECU turns the cruise control off.

If the harness connected to terminal STP– has an open circuit, terminal STP– will have battery positive
voltage and the cruise control will be turned off.

Also, when the brake is on, the magnetic clutch circuit is cut mechanically by the stop light switch, turning
the cruise control off. (See page

DI–490

for operation of the magnetic clutch)

WIRING DIAGRAM

See page

DI–490

.

DI0EZ–01

Input Signal

Indicator Light
Blinking Pattern

Stop Light
switch ON

Light

OFF

ON

SW OFF

SW ON

DI–506

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

658

1997 LEXUS ES300 (RM511U)

INSPECTION PROCEDURE

1

Check operation of stop light.

CHECK:
Check that stop light comes on when brake pedal is depressed, and turns off when brake pedal is released.

NG

Check stop light system (See page

BE–2

).

OK

2

Input signal check.

CHECK:
(a)

See input signal check on

DI–478

.

(b)

Check the indicator light when the brake pedal is de-
pressed.

OK:

The indicator light goes off when the brake pedal is
depressed.

OK

Proceed to next circuit inspection shown on
problem symptom table (See page

DI–487

).

NG

AB0119
N19915

I00741

ON

STP–

(–)

(+)

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–507

659

1997 LEXUS ES300 (RM511U)

3

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

PREPARATION:
(a)

Remove the ECU with connectors still connected.

(b)

Turn ignition switch ON.

CHECK:
Measure voltage between terminal STP– of cruise control ECU
connector and body ground, when the brake pedal is de-
pressed and released.
OK:

Depressed

10 – 14 V

Released

Below 1 V

OK

Proceed to next circuit inspection shown on
problem symptom table (See page

DI–487

).

NG

4

Check for open in harness and connectors between terminal STP– of cruise con-
trol ECU and stop light switch (See page

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace cruise control ECU
(See page

IN–27

).

N21221

Cruise Control ECU

14

OD

6

ECT

L–R

7

OD1

17

11

S2

L–B

L–B

Junction
Connector

Electronically
Controlled
Transmission
No.2 Solenoid

J26

A

A

A

ECM

Y–B

IK2

7

C14

C14

E7

E10

E10

S1

E3

L–B

V

W

3

6

DI–508

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

660

1997 LEXUS ES300 (RM511U)

Electronically Controlled Transmission Communication Circuit

CIRCUIT DESCRIPTION

When driving uphill under cruise control, in order to reduce shifting due to ON–OFF overdrive operation and
to provide smooth driving, when down shifting in the electronically controlled transmission occurs, a signal
to prevent upshift until the end of the up hill slope is sent from the cruise control ECU to the electronically
controlled transmission.
Terminal ECT of the cruise control ECU detects the shift change signal (output to electronically controlled
transmission No. 2 solenoid) from the ECM.
If vehicle speed down, also when terminal ECT of the cruise control ECU receives down shifting signal, it
sends a signal from terminal OD to ECM to cut overdrive until the end of the uphill slope, and the gear shifts
are reduced and gear shift points in the electronically controlled transmission are changed.

WIRING DIAGRAM

DI0F2–01