Lexus RX300 (MCU15). Service manual - part 299

H01370
H08058

H16266

Airbag
Sensor
Assembly

Front Airbag Sensor (LH)

(+)

+SL

(–)

–SL

Airbag Sensor
Assembly

H09526
H08058

H16267

Front Airbag
Sensor (LH)

Airbag
Sensor
Assembly

(+)

+SL

Airbag Sensor
Assembly

(–)

–SL

DI–428

–

DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

LEXUS RX300   (RM785E)

4

Check wire harness.

CHECK:
For the connector (on the airbag sensor assembly side) be-
tween the front airbag sensor (LH) and the airbag sensor as-
sembly, measure the resistance between +SL and –SL.
OK:

Resistance: 1 MΩ or Higher

NG

Repair or replace harness or connector be-
tween front airbag sensor (LH) and airbag sen-
sor assembly.

OK

5

Check wire harness.

PREPARATION:
Using a service wire, connect +SL and –SL of the connector (on
the front airbag sensor (LH) side) between the airbag sensor
assembly and the front airbag sensor (LH).
CHECK:
For the connector (on the airbag sensor assembly side) be-
tween the front airbag sensor (LH) and the airbag sensor as-
sembly, measure the resistance between +SL and –SL.
OK:

Resistance: Below 1 Ω

NG

Repair or replace harness or connector be-
tween front airbag sensor (LH) and airbag sen-
sor assembly.

OK

H01009

H01371

H01155

Airbag
Sensor
Assembly

Front Airbag Sensor (LH)

(+)

+SL

(–)

–SL

–

DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

DI–429

LEXUS RX300   (RM785E)

6

Check front airbag sensor (LH).

CHECK:.
For the connector (on the front airbag sensor (LH)), measure
the resistance between +SL and –SL.
OK:

Resistance: 300 – 1500 Ω

NG 

Replace front airbag sensor (LH).

OK

AB0119

H01369

H01063

H10600

H16268

Front Airbag
Sensor (LH)

Airbag
Sensor
Assembly

ON

DTC B1158/B1159/16

DLC3

CG

Tc

→ ←

→ ←

DI–430

–

DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

LEXUS RX300   (RM785E)

7

Check airbag sensor assembly.

PREPARATION:
(a)

Turn the ignition switch to LOCK.

(b)

Disconnect negative (–) terminal cable from the battery,
and wait at least for 90 seconds.

(c)

Connect the front airbag sensor (LH) connector and air-
bag sensor assembly connector.

(d)

Connect negative (–) terminal cable to the battery, and
wait at least for 2 seconds.

CHECK:
(a)

Turn the ignition switch to ON, and wait at least for 20 se-
conds.

(b)

Clear the DTC stored in memory (See page DI–305).

(c)

Turn the ignition switch to LOCK, and wait at least for 20
seconds.

(d)

Turn the ignition switch to ON, and wait at least for 20 se-
conds.

(e)

Check the DTC (See page DI–305).

OK:

DTC B1158/B1159/16 is not output.

HINT:
Codes other than code B1158/B1159/16 may be output at this
time, but they are not relevant to this check.

NG 

Replace airbag sensor assembly.

OK

From the results of the above inspection, the malfunctioning part can now be considered normal.
To make sure of this, use the simulation method to check.

H17181

Battery

40A AM1

F11 FL Block

7.5A IGN

6

Instrument Panel J/B

I15 Ignition SW

3

W

B

Engine Room J/B

4

1

B–Y

2

W–L

7

W–R

3

1C

6

7

1

6

1

12

1G

W

W–L (*1)
W–R (*2)

GR

B–O

A28

6

5

IG1

IG2

2I

6

2C

W

1

5

140A ALT

1A

1L

1L

1C

1C

1C

15A SRS–IG

Airbag Sensor Assembly

20A AM2

1

1

2

IG2

IG1

AM2

AM1

A28

*1: LHD
*2: RHD

Instrument Panel J/B

A28

27

28

E1

E2

A28

W–B

W–B

W–B

W–B

A

A

A

J7
J/C

J9
J/C

1L

9

1L

10

1E

4

14

1D

IF

IG

–

DIAGNOSTICS

SUPPLEMENTAL RESTRAINT SYSTEM

DI–431

LEXUS RX300   (RM785E)

DTC

Normal

Source Voltage Drop

CIRCUIT DESCRIPTION

The SRS is equipped with a voltage–increase circuit (DC–DC converter) in the airbag sensor assembly in
case the source voltage drops. 
When the battery voltage drops, the voltage–increase circuit (DC–DC converter) functions to increase the
voltage of the SRS to normal voltage. 
The diagnosis system malfunction display for this circuit is different from other circuits that is when the SRS
warning light remains lit up and the DTC is a normal code, source voltage drop is indicated. 
Malfunction in this circuit is not recorded in the airbag sensor assembly, and the source voltage returns to
normal, the SRS warning light automatically goes off.

DTC No.

Diagnosis

(Normal)

Source voltage drop

WIRING DIAGRAM

DI6PY–09