SRS Description

SRS Components


Airbags

The SRS is a safety device which, when used with the seat belt, is designed to help protect the driver and front passenger in a frontal impact exceeding a certain set limit. The system consists of the SRS unit, including safing sensor and impact sensor (A), the cable reel (B), the driver's airbag (C), the front passenger's airbag (D), side airbags (E), seat belt tensioners (G), right side seat belt outer lap tensioner (H), left side seat belt outer lap tensioner (I) and front impact sensors (J).

 

Side Airbags

The side airbags (E) are in each front seat-back. They help protect the upper torso of the driver or front seat passenger during a moderate to severe side impact. Side impact sensors (first) (F) in each door sill and in the SRS unit detect such an impact and instantly inflate the driver's or the passenger's side airbag. Only one side airbag will deploy during a side impact. If the impact is on the passenger's side, the passenger's side airbag will deploy even if there is no passenger.

Side Curtain Airbags

The side curtain airbags (K) are in each side of the roof. They help protect the head of the driver or door side passenger during a moderate to severe side impact. Side impact sensors (first) (F) in each front door sill, side impact sensors (second) (L) in each rear door sill, and the SRS unit detect such an impact and instantly inflate the driver's or the passenger's side curtain airbag. A side impact at the vehicle causes the side curtain airbag and the side airbag on the impacted side to deploy at the same time.

Seat Belt Tensioners/Seat Belt Outer Lap Tensioner

The seat belt tensioners are linked with the SRS airbags to further increase the effectiveness of the seat belt. In a front-end collision, the tensioners instantly retract the belt firmly to secure the occupants in their seats.

SRS Operation


The main circuit in the SRS unit senses and judges the force of impact and, if necessary, ignites the inflator charges. If battery voltage is too low or power is disconnected due to the impact, the voltage regulator and the back-up power circuit, respectively, will keep voltage at a constant level.

For the SRS to operate:


Seat Belt Tensioners/Seat Belt Outer Lap Tensioner

(1) A front impact sensor must activate and send electric signals to the microprocessor.
(2) The microprocessor must compute the signals and send them to the tensioners.
(3) The charges must ignite and deploy the tensioners.

Driver's and Front Passenger's Airbag(s)

(1) A front impact sensor must activate, and send electric signals to the microprocessor.
(2) The microprocessor must compute the signals, and send them to the airbag inflator(s).
(3) The inflators that received signals must ignite and deploy the airbags.

NOTE: When the side curtain airbag deployed, the seat belt tensioners are also deployed at the same time.

Side Airbag(s)

(1) A side impact sensor and satellite safing sensor must activate, and send electric signals to the microprocessor.
(2) The microprocessor must compute the signals and send them to the side airbag inflator(s). However, the microprocessor cuts off the signals to the front passenger's side airbag if the SRS unit determines that the front passenger's head is in the deployment path of the side airbag.
(3) The inflator that received the signal must ignite and deploy the side airbag.

Side Curtain Airbag(s)

(1) Side impact sensors and satellite safing sensor must activate, and send electrical signals to the microprocessor.
(2) The microprocessor must compute the signals and send them to the side curtain airbag and side airbag inflator(s).
(3) The inflator that received the signals must ignite and deploy the side curtain airbag and side airbag at the same time.

 

Self-diagnosis System

A self-diagnosis circuit is built into the SRS unit; if the SRS is operating normally when the ignition switch is turned ON (II), the SRS indicator comes on and goes off after about 6 seconds.
If the indicator does not come on, or does not go off after 6 seconds, or if it comes on while driving, it indicates an abnormality in the system. The system must be inspected and repaired as soon as possible.

For better serviceability, the SRS unit memory stores a DTC that relates to the cause of the malfunction, and the unit is connected to the data link connector (DLC). This information can be read with the HDS when it is connected to the DLC (16P).

NOTE: Before you disconnect the negative cable from the battery for troubleshooting, make sure you have the anti-theft code for the radio. Write down the audio presets.

SRS Unit Inputs and Outputs at Connector A (28P)

 

Terminal Number Wire Color Terminal Name Description 
1 GRN LA2+ Power source for driver's airbag second inflator 
2 PUR LA2- Ground for driver's airbag second inflator 
3 LT GRN RA2+ Power source for passenger's airbag second inflator 
4 LT BLU RA2- Ground for passenger's airbag second inflator 
5 LT GRN MES Memory delete signal input 
6 ORN SCS Service check signal input 
7 LT BLU LA1+ Power source for driver's airbag first inflator 
8 BRN LA1- Ground for driver's airbag first inflator 
9 YEL RA1+ Power source for passenger's airbag first inflator 
10 BLU RA1- Ground for passenger's airbag first inflator 
11 WHT CAN HI Sends and receives communication signal 
12 RED CAN LO Sends and receives communication signal 
13 ——— Not used ——— 
14 GRN OPDS Sends and receives communication signal 
15 BRN LFS- Ground for left front impact sensor 
16 LT BLU RFS- Ground for right front impact sensor 
17 YEL VA SRS system sub power (common with OPDS) 
18 RED VB SRS dedicated power (dedicated booster circuit) 
19 ——— Not used ——— 
20 ——— Not used ——— 
21 ——— Not used ——— 
22 BLK SRS GND (1) Ground circuit for the SRS 
23 BLK SRS GND (2) Ground circuit for the SRS 
24 LT BLU K-LINE Sends and receives scan tool signal 
25 ——— Not used ——— 
26 ——— Not used ——— 
27 RED LFS+ Power source for left front impact sensor 
28 GRN RFS+ Power source for right front impact sensor 

SRS Unit Inputs and Outputs at Connector B (28P)

 

Terminal Number Wire Color Terminal Name Description 
1 RED LRP+ Power source for left side seat belt tensioner 
2 BRN LRP- Ground for left side seat belt tensioner 
3 GRN RRP+ Power source for right side seat belt tensioner 
4 LT BLU RRP- Ground for right side seat belt tensioner 
5 GRY SS- Ground for seat sitting switch 
6 LT GRN SS+ Power source for seat sitting switch 
7 ORN LBP+ Power source for left side buckle tensioner 
8 GRN LBP- Ground for left side buckle tensioner 
9 YEL RBP+ Power source for right side buckle tensioner 
10 WHT RBP- Ground for right side buckle tensioner 
11 YEL LBSC Left side seat belt buckle switch un-buckled signal 
12 LT GRN LBSO Left side seat belt buckle switch buckled signal 
13 ——— Not used ——— 
14 ——— Not used ——— 
15 BLU RBSC Right side seat belt buckle switch un-buckled signal 
16 ORN RBSO Right side seat belt buckle switch buckled signal 
17 GRN LSA+ Power source for left side airbag inflator 
18 RED LSA- Ground for left side airbag inflator 
19 WHT RSA+ Power source for right side airbag inflator 
20 BLU RSA- Ground for right side airbag inflator 
21 BRN LCA1+ Power source for left side curtain airbag inflator 
22 BLU LCA1- Ground for left side curtain airbag inflator 
23 GRY RCA1+ Power source for right side curtain airbag inflator 
24 RED RCA1- Ground for right side curtain airbag inflator 
25 PNK LBS1+ Power source for left side impact sensor (first), left side impact sensor (second) and rear safing sensor 
26 BLU LBS1- Ground for left side impact sensor (first), left side impact sensor (second) and rear safing sensor 
27 BRN RBS1+ Power source for right side impact sensor (first), right side impact sensor (second) 
28 YEL RBS1- Ground for right side impact sensor (first), right side impact sensor (second)