Lexus ES300 (2002 year). Service manual — part 90

BODY ELECTRICAL – ACCESSORIES

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208BE59

Collision

Impact

Collision

Impact

Front Airbag Sensors

Seat Position
Sensor (Driver)

Airbag Sensor
Assembly

Side and
Curtain
Shield Airbag
Sensor
Assembly

Driver
Seat Belt
Buckle Switch

Curtain
Shield Airbag
Sensor
Assembly

Inflator (For Driver and

Front Passenger)

Seat Belt Pretensioner

(LH and RH)

Inflator
(For Left Side and
Left Curtain Shield)

Inflator
(For Right Side and
Right Curtain Shield)

Inflator
(For Left Curtain Shield)

Inflator
(For Right Curtain Shield)

SRS AIRBAG SYSTEM

1. General

The SRS (Supplemental Restraint System) airbag are provided for the driver and front passenger. The SRS

airbags have been designed to help reducing the shocks to the heads and chests of the driver and front pas-
senger in the event of a severe frontal impact collision as supplements to the seat belts.
This system is a 3-sensor type airbag system to detect the impact during a front collision using the airbag
sensor assembly and front airbag sensors, and to make the airbag system and seat belt pretensioner operate
as well.

On the ’02 ES300, the previous mechanical type front airbag sensor assembly (consisting of movable and

stationary contact points) has been changed to an electrical (deceleration sensor) type front airbag sensor
assembly.

Dual-stage SRS airbags system, that controls the airbag inflating output optimum by judging the extent

of impact, seat position and whether or not the seat belt is fasten, has been adopted for the driver and front
passenger airbags.

In accordance with the adoption of the dual-stage SRS airbags system, a seat position sensor has been es-

tablished for the driver seat.

On the ’02 ES300, a curtain shield airbag system that helps reduce the impact applied to the front and rear

seat occupants with a single curtain shield airbag has been adopted.
In conjunction with this system, a side and curtain shield airbag sensor assembly has been provided at the
bottom of the center pillar and a curtain shield airbag sensor assembly at the bottom of the rear pillar.

In this system, a front side collision is detected by the side and curtain shield airbag sensor assembly in

order to simultaneously deploy the side and curtain shield airbags. A rear side collision is detected by the
curtain shield airbag sensor assembly and the airbag sensor assembly in order to deploy only the curtain
shield airbag.

The function of the airbag sensor assembly to memorize the driver and front passenger’s seat belt wearing

condition while inflating the airbag is added.

System Diagram

BODY ELECTRICAL – ACCESSORIES

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211BE36

Front Airbag
Sensor (LH)

SRS Warning
Light

Front Airbag
Sensor (RH)

Curtain Shield
Airbag Assembly (LH)

Front Passenger
Airbag Assembly

Curtain Shield
Airbag Assemble (RH)

Side Airbag
Assembly (RH)

Side and Curtain
Shield Airbag Sensor
Assembly (RH)

Curtain Shield
Airbag Sensor
Assembly (RH)

Seat Belt
Pretensioner (RH)

Airbag Sensor Assembly

Driver Seat Belt
Buckle Switch

Curtain Shield Airbag
Sensor Assembly (LH)

Seat Position Sensor
(Driver Seat Only)

Side Airbag
Assembly (LH)

Seat Belt
Pretensioner (LH)

Side and Curtain
Shield Airbag
Sensor Assembly (LH)

Driver Airbag
Assembly

2. Layout of Main Components

BODY ELECTRICAL – ACCESSORIES

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Service Tip

In accordance with the structure change of the driver and front passenger inflators on ’02 ES300, a SST
(09082-00800) used for scrapping driver and front passenger airbag assemblies of the vehicle has been
newly established.

208BE40

Seat Position Sensor

Seat Position
Sensor

Magnet
Portion

Seat Rail

Hall IC

Shielding
Plate

A – A Cross Section

A

A

211BE64

Seat position is rearward

Seat position is forward

Seat Position
Sensor

Shielding
Plate

Rearward

Forward

View of Backside

3. Dual-stage SRS Airbags System

General

In this system, when the front airbag sensors and the airbag sensor assembly detect the front collision, the
airbag sensor assembly judges the extent of impact, seat position and whether or not the seat belt is fasten,
thus making the airbag inflating output optimum by delaying the inflating timing of the 2nd initiator and
the 1st initiator.

Seat Position Sensor
The seat position sensor, which is attached to the seat rail of the driver seat, detects the sliding position

of the seat. In addition, the shielding plate to make the seat position sensor judge the seat position is
installed on this seat rail.

The seat position sensor use a Hall IC for its sensor and has magnet portion on its opposite side.

The seat position detection by the seat position sensor judges that the seat position is rearward if the shielding

plate is between the sensor and the seat position is forward if the shielding plate is not between the sensor.

BODY ELECTRICAL – ACCESSORIES

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4. Self-Diagnosis Function

If the airbag sensor assembly detects a malfunction in the SRS airbag system, the airbag sensor assembly

stores the malfunction data in memory, in addition to illuminating the SRS warning light. Then, the DTCs
(Diagnostic Trouble Codes) can be accessed by connecting a hand-held tester to the DLC3 terminal or the
SST (09843-18040) to the Tc and CG terminals of the DLC3 and reading the blinking of the SRS warning
light. For further details, see the 2002 LEXUS ES300 Repair Manual (Pub. No. RM911U).

The following DTC is newly added.

DTC No.

Detection Item

DTC No.

Detection Item

B1180 / 17

Short in D squib (2nd step) circuit

B1149 / 37

Front airbag sensor (LH)
malfunction

B1181 / 18

Open in D squib (2nd step) circuit

B1154 / 38

Curtain shield airbag sensor
assembly (RH) malfunction

B1182 / 19

Short in D squib (2nd step) circuit
(to ground)

B1155 / 39

Curtain shield airbag sensor
assembly (LH) malfunction

B1183 / 22

Short in D squib (2nd step) circuit
(to B+)

B1187 / 55

Short in P squib (2nd step) circuit
(to ground)

B1153 / 25

Seat position sensor assembly
malfunction

B1188 / 56

Short in P squib (2nd step) circuit
(to B+)

B0126 / 27

Seat belt buckle switch (LH)
malfunction

B1185 / 57

Short in P squib (2nd step) circuit

B0127 / 27

Seat belt buckle switch (LH)
malfunction

B1186 / 58

Open in P squib (2nd step) circuit

B1148 / 36

Front airbag sensor (RH)
malfunction

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