Lexus RX300 (MCU15). Manual — part 307

I11488

HORN

(+)

(–)

DI–460

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

LEXUS RX300 (RM785E)

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
(See page IN–32).

OK

Check and replace theft deterrent ECU
(See page IN–32).

I19245

Theft Deterrent ECU

U1
Unlock Warning SW

W–B

L

IF

19

T4

KSW

A

2

1

A

W–B

J7
J/C

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

DI–461

LEXUS RX300 (RM785E)

Key Unlock Warning Switch Circuit

CIRCUIT DESCRIPTION

The key unlock warning switch goes ON when the ignition key is inserted in the key cylinder and goes OFF
when the ignition key is removed.
The ECU operates the key confinement prevention function while the key unlock warning switch is ON.

WIRING DIAGRAM

DI61F–04

2 1

e–4–2–B

I11309

DI–462

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

LEXUS RX300 (RM785E)

INSPECTION PROCEDURE

1

Check key unlock warning switch.

PREPARATION:
Disconnect key unlock warning switch connector.
CHECK:
Check continuity between terminal 1 and 2 of key unlock warn-
ing switch connector, when the key is inserted into the key cylin-
der or removed.
OK:

Switch position

Tester connection

Specified condition

ON (Key inserted)

1 – 2

Continuity

OFF (Key removed)

–

No continuity

NG

Replace key unlock warning switch.

OK

2

Check harness and connectors between ECU and key unlock warning switch,
key unlock warning switch and body ground (See page IN–32).

NG

Repair or replace harness or connector.

OK

Check and replace theft deterrent ECU.*1

*1: When there is a malfunction that the theft deterrent system cannot be set, proceed to the next numbered
circuit inspection shown in problem symptom table (See page DI–452).

I19246

Theft Deterrent ECU

L2

13

L–W

5

8

Lock

B10
Back Door Key Lock
and Unlock SW

T4

A

J14
J/C

IA2

L–W

2

1

W–B

BN

Unlock

BC2

L–W

LU2

5

6

7

T4

IA2

3

BC2

LG–R

LG–R

LG–R

–

DIAGNOSTICS

THEFT DETERRENT SYSTEM

DI–463

LEXUS RX300 (RM785E)

Back Door Key Lock and Unlock Switch Circuit

CIRCUIT DESCRIPTION

The back door key lock and unlock switch goes ON when the back door key cylinder is turned to the unlock
side with the key.

WIRING DIAGRAM

DI84V–01