Lexus ES300 (1997 year). Service manual - part 409

N22062

Theft Deterrent ECU

SH

T3

3

5

4

Theft Deterrent
Horn

1

2

3

10A HORN

1

E/G Room J/B

FL BLOCK

FL MAIN
3.0W

Battery

1

1

W–L

W–L

W–L

W

IJ1

IM1

2F

2A

F8

F6

B–G

B

N14681

1(+)

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

DI–413

565

1997 LEXUS ES300   (RM511U)

Theft Deterrent Horn Circuit

CIRCUIT DESCRIPTION

When the theft deterrent system is activated, contact (a) and contact (b) in the ECU close alternately in cycles
of approximately 0.2 sec., causing the theft deterrent horn to blow (See the wiring diagram below).
In this condition, if any of the following operations is done, the contact (a) in the ECU opens, thus stopping
the theft deterrent horn from blowing:

(1)

Unlock the front LH or RH door with key.

(2)

Turn the ignition switch to ACC or ON position.

(3)

Unlock the doors with the wireless door lock control system.

(4)

Wait for approximately 60 seconds.

WIRING DIAGRAM

INSPECTION PROCEDURE

1

Check voltage between terminal 1 of theft deterrent horn connector and body
ground.

PREPARATION:
Remove the theft deterrent horn and disconnect the connector.
CHECK:
Measure voltage between terminal 1 of theft deterrent horn
connector and body ground.
OK:

Voltage: 10

∼

14V

DI01Y–01

N14682

1 (–)

2 (+)

DI–414

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

566

1997 LEXUS ES300   (RM511U)

NG

Check and repair harness and connector be-
tween HORN fuse and theft deterrent horn.

OK

2

Check theft deterrent horn.

CHECK:
Connect positive (+) lead to terminal 1 and negative (–) lead to
terminal 2 to theft deterrent horn connector.
OK:

Theft deterrent horn blows.

NG

Replace theft deterrent horn.

OK

3

Check harness and connector between theft deterrent ECU and theft deterrent
horn (See page 

IN–27

).

NG

Check and repair harness or connector.

OK

Check and replace theft deterrent ECU.

N22063

Theft Deterrent ECU

HORN

6

11

A

A

J/C J2

G–W

Horn
RH

E/G Room J/B

HORN Relay

3

1

10

2

5

1

10A HORN

1

1

FL BLOCK

1

FL MAIN
3.0W

Battery

A

Horn
LH

G–W

6

Horn Switch

T3

IG1

G–B

G–B

G–B

B–G

B

F8

F6

2A

2K

2F

G–W

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

DI–415

567

1997 LEXUS ES300   (RM511U)

Horn Relay Circuit

CIRCUIT DESCRIPTION

When the theft deterrent system is activated, it causes the Tr in the ECU to switch on and off in approximately
0.4 sec. cycles. This switches the horn relay on and off, thus the horns blow (See the wiring diagram below).
In this condition, if any of the following operations is done, the Tr in the ECU goes off and the horn relay
switches off, thus stopping the horns from blowing:

(1)

Unlock the front LH or RH door with key.

(2)

Turn the ignition switch to ACC or ON position.

(3)

Unlock the doors with the wireless door lock control system.

(4)

Wait for approximately 60 seconds.

WIRING DIAGRAM

DI01Z–01

N20678

HORN

(+)

(–)

DI–416

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

568

1997 LEXUS ES300   (RM511U)

INSPECTION PROCEDURE

HINT:
The flow chart below is based on the premise that the horns blow normally whenever the horn switch is oper-
ated. If horn operation is not normal when the horn switch is operated, check the horn switch.

1

Check voltage between terminal HORN of theft deterrent ECU connector and
body ground.

PREPARATION:
Disconnect the theft deterrent ECU connectors.
CHECK:
Measure voltage between terminal HORN of theft deterrent
ECU connector and body ground.
OK:

Voltage: 10

∼

14V

NG

Check and repair harness and connector be-
tween theft deterrent ECU and horn relay.

OK

Check and replace theft deterrent ECU.