Parts for Electrical Circuit
Wiring – Wire color
All wires have color–coded insulation.
Wires belonging to a system’s main harness will have a
single color (1). Wires belonging to a system’s subcircuits
will have a colored stripe (2). Striped wires use the
following code to show wire size and colors.
Example: 0.5 G / R
Red (Stripe color)
Green (Base color)
Wire size (0.5 mm
2)
Wiring – Wire Color Coding
Abbreviations are used to indicate wire color within a circuit diagram.
Refer to the following table.
Color Coding Meaning Color Coding Meaning
B Black BR Brown
W White LG Light green
RRedGRGrey
G Green P Pink
Y Yellow LB Light blue
LBlue VViolet
OOrange
1
2
Fuse
Fuses are the most common form of circuit protection
used in vehicle wiring. A fuse is a thin piece of wire or strip
of metal encased in a glass or plastic housing. It is wired
in series with the circuit it protects. When there is an
overload of current in a circuit, such as a short of a ground,
the metal strip is designed to burn out and interrupt the
flow of current. This prevents a surge of high current from
reaching and damaging other components in the circuit.
Determine the cause of the overloaded before replacing
the fuse.
The replacement fuse must have the same amperage
specification as the original fuse.
Never replace a blown fuse with a fuse of a different
amperage specification.
Doing so can result in an electrical fire or other serious
circuit damage. A blown fuse is easily identified as shown
in the figure.
Fusible Link
The fusible link is primarily used to protect circuits where
high amounts of current flow and where it would not be
practical to use a fuse. For example, the starter circuit.
When a current overload occurs, the fusible link melts
open and interrupts the flow of current so as to prevent
the rest of the wiring harness from burning.
Determine the cause of the overload before replacing the
fusible link. the replacement fusible link must have the
same amperage specification as the original fusible link.
Never replace a blown fusible link with fusible link of a
different amperage specification. Doing so can result in
an electrical fire or other serious circuit damage.
A blown fusible link is easily identified as shown in the
figure.
Fusible Link Specifications
Type Rating Case Color Maximum Circuit Current (A)
Connector 30A Pink 15
Connector 40A Green 20
Bolted 50A Red 25
Bolted 60A Yellow 30
Bolted 80A Black 40
SUPPLEMENTAL RESTRAINT SYSTEM9J–3
System Description
The SRS consists of the Sensing and Diagnostic Module
(SDM), the driver air bag assembly, the SRS coil
assembly, the passenger air bag assembly and the “AIR
BAG” warning lamp in the instrument cluster. The SDM,
SRS coil assembly (driver side only), driver air bag
assembly, passenger air bag assembly and connector
wire make up the deployment loops. The function of the
deployment loops is to supply current through air bag
assembly, which will cause deployment of the air bags in
the event of a frontal crash of sufficient force, up to 30degrees off the centerline of the vehicle. The air bag
assemblies are only supplied enough current to deploy
when the SDM detects vehicle velocity changes severe
enough to warrant deployment.
The SDM contains a sensing device which converts
vehicle velocity change to an electrical signal. The
electrical signal generated is processed by the SDM and
then compared to a value stored in memory. When the
generated signal exceeds the stored value, the SDM will
cause current to flow through the air bag assembly
deploying the air bags.
D09RW014
SUPPLEMENTAL RESTRAINT SYSTEM9J–5
1. Energy Reserve — The SDM maintains 24–Volt Loop
Reserve (24VLR) energy supply to provide
deployment energy when ignition voltage is lost in a
frontal crash.
2. Frontal Crash Detection — The SDM monitors
vehicle velocity changes to detect frontal crashes
which are severe enough to warrant deployment.
3. Air Bag Deployment — When a frontal crash of
sufficient force is detected, the SDM will cause
enough current to flow through the air bag assembly
to deploy the air bag.
4. Malfunction Detection — The SDM performs
diagnostic monitoring of SRS electrical components
and sets a diagnostic trouble code when a
malfunction is detected.
5. Frontal Crash Recording — The SDM records
information regarding SRS status during frontal
crash.
6. Malfunction Diagnosis — The SDM displays SRS
diagnostic trouble codes and system status
information through the use of a scan tool.
7. Driver Notification — The SDM warns the vehicle
driver of SRS malfunctions by controlling the “Air
Bag” warning lamp.
The SDM is connected to the SRS wiring harness by a
24–pin connector. This harness connector uses a
shorting clip across certain terminals in the contact area.
This shorting clip connects the “AIR BAG” warning lamp
to ground when the SDM harness connector is
disconnected or CPA (Connector Position Assurance) is
not inserted even if completely connected. This will
cause the “AIR BAG” warning lamp to come “ON” steady
whenever the ignition switch is at the ON or START
positions with the SDM disconnected.
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Legend
(1) SDM
(2) SRS Harness
(3) Connector Position Assurance
“Air Bag” Warning Lamp
Ignition voltage is applied to the “AIR BAG” warning lamp
when the ignition switch is at the ON or START positions.
The SDM controls the lamp by providing ground with a
lamp driver. The “AIR BAG” warning lamp is used in the
SRS to do the following:
1. Verify lamp and SDM operation by turn on 3.5
seconds and then turns “OFF” when the ignition
switch is first turned “ON”.
2. Warn the vehicle driver of SRS electrical system
malfunctions which could potentially affect the
operation of the SRS. These malfunctions could
result in nondeployment in case of a frontal crash or
deployment for conditions less severe than intended.
The “AIR BAG ” warning lamp is the key to driver
notification of SRS malfunctions. For proper lamp
operation, refer to the “SRS Diagnostic System Check” in
this section.
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SRS Coil Assembly
The SRS coil assembly consists of two current carrying
coils. This is attached to the steering column and allow
rotation of the steering wheel while maintaining
continuous contact of the driver deployment loop to the
driver air bag assembly.
There is a shorting clip on the yellow 2–pin connector near
the base of steering column which connects the SRS coil
to the SRS wiring harness.
The shorting clip shorts to the SRS coil and driver air bag
assembly when the yellow 2–pin connector is
disconnected. The circuit to the driver air bag assembly is
shorted in this way to help prevent unwanted deployment
of the air bag when servicing the steering column or other
SRS components.
SUPPLEMENTAL RESTRAINT SYSTEM9J–7
Steering Column
The steering column absorbs energy and is designed to
compress in a frontal crash to decrease the chance of
injury to the driver.
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Knee Bolster
The knee bolsters are used to absorb energy to protect
knees and control the forward movement of the vehicle’s
front seat occupants during a frontal crash, by limiting leg
movement.
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Definitions
Air Bag
An inflatable cloth cushion designed to deploy in certain
frontal crashes. It supplements the protection offered by
the seat belts by distributing the impact load more evenly
over the vehicle occupant’s head and torso.
Asynchronous
Performed in a nonperiodic fashion, (i.e., no defined time
or interval).B+
Battery voltage, (B+) The voltage available at the battery
at the time of the indicated measurement. With the key
“ON” and the engine not running, the system voltage will
likely be between 12 and 12.5 volts. At idle, the voltage
may be 14 to 16 volts. The voltage could be as low as 10
volts during engine cranking.
Bulb Check
The SDM will cause the “AIR BAG” warning lamp to turn
on 3.5 seconds and then go “OFF” whenever the ignition
switch transitions to the ON position from any other
ignition switch position and no malfunctions are detected.
“Continuous Monitoring”
Tests performed by the SDM on the SRS every 100
milliseconds while “Ignition 1” voltage is in the normal
operating voltage range at the SDM.
Data Link Connector (DLC)
Formerly “DLC” a connector which allows communication
with an external computer, such as a scan tool.
Datum Line
A base line parallel to the plane of the underbody or frame
from which all vertical measurements originate.
Deploy
To inflate the air bag.
Deployment Loops
The circuits which supply current to the air bag
assemblies to deploy the air bag.
Diagnostic Trouble Code (DTC)
Formerly “Code”, a numerical designator used by the
SDM to indicate specific SRS malfunctions.
Driver Current Source
An output of the SDM which applies current into the driver
air bag assembly circuit during the “Initiator Assembly
Resistance Test”.
Driver Air Bag Assembly
An assembly located in the steering wheel hub consisting
of an inflatable bag, an inflator and an initiator.
EEPROM
Electrically Erasable Programmable Read Only Memory.
Memory which retains its contents when power is
removed from the SDM.
Ignition Cycle
The voltage at the SDM “Ignition 1” inputs, with ignition
switch “ON”, is within the normal operating voltage range
for at least ten seconds before turning ignition switch
“OFF”.
Ignition 1
A battery voltage (B+) circuit which is only powered with
the ignition switch in the ON, or START positions.
Initiator
The electrical component inside the air bag assembly
which, when sufficient current flows, sets off the chemical
reaction that inflates the air bag.
“Initiator Assembly Resistance Test”
Tests performed once each ignition cycle when no
malfunctions are detected during “Turn–ON” or
“Continuous Monitoring”. This test checks for the correct
SDM configuration for the vehicle, shorts to “Ignition 1” in
SUPPLEMENTAL RESTRAINT SYSTEM 9J–8
the deployment loops, high resistance or opens in the
“Driver Side High”, “Driver Side Low”, “Passenger Side
High” and “Passenger Side Low” circuits and measures
the resistance of the inflator assembly consisting of 1)
Initiators, 2) SRS coil assembly (driver side only), 3)
Connectors and associated wiring.
Normal Operating Voltage Range
The voltage measured between the SDM “Ignition 1”
terminals and “Ground” terminals is between 9 and 16
volts.
Passenger Current Source
An output of the SDM which applies current into the
passenger air bag assembly circuit during the “Initiator
Assembly Resistance Test”.
Passenger Air Bag Assembly
An assembly located in the right side of the instrument
panel consisting of an inflatable bag, an inflator and an
initiator.
Scan Tool
An external computer used to read diagnostic information
from on–board computers via the data link connector.
SDM
Sensing and Diagnostic Module which provides reserve
energy to the deployment loops, deploys the air bags
when required and performs diagnostic monitoring of all
SRS components.
Serial Data
Information representing the status of the SRS.
SRS
Supplemental Restraint System.
SRS Coil Assembly
An assembly of two current–carrying coils in the driver
deployment loop that allows the rotation of the steering
wheel while maintaining the continuous contact of the
driver deployment loop to the driver air bag assembly.
SRS Wiring Harness
The wires and connectors that electrically connect the
components in the SRS.
“Turn–ON”
Test which the SDM performs on the SRS once during
each ignition cycle immediately after “Ignition 1” voltage
is applied to the SDM and before “Continuous
Monitoring”.
Diagnosis
WARNING: TO AVOID DEPLOYMENT WHEN
TROUBLESHOOTING THE SRS, DO NOT USE
ELECTRICAL TEST EQUIPMENT SUCH AS A
BATTERY–POWERED OR AC–POWERED
VOLTMETER, OHMMETER, ETC., OR ANY TYPE OF
ELECTRICAL EQUIPMENT OTHER THAN THAT
SPECIFIED IN THIS MANUAL. DO NOT USE A
NONPOWERED PROBE–TYPE TESTER.
INSTRUCTIONS IN THIS MANUAL MUST BE
FOLLOWED CAREFULLY, OTHERWISE PERSONAL
INJURY MAY RESULT.
Diagnostic Trouble Codes
The “SRS Diagnostic System Check” must always be the
starting point of any SRS diagnosis. The “SRS
Diagnostic System Check” checks for proper “AIR BAG”
warning lamp operation and checks for SRS diagnostic
trouble codes using the scan tool.
1. Current diagnostic trouble codes – Malfunctions that
are presently being detected. Current diagnostic
trouble codes are stored in RAM (Random Access
Memory).
2. History diagnostic trouble codes – All malfunctions
detected since the last time the history memory was
cleared. History diagnostic trouble codes are stored
in EEPROM.
Scan Tool Diagnostics
A scan tool is used to read current and history diagnostic
trouble codes and to clear all diagnostic trouble codes
after a repair is completed. The scan tool must be
updated to communicate with the SRS through a
replaceable cartridge before it can be used for SRS
diagnostics. To use the scan tool, connect it to the data
link connector and turn the ignition switch “ON”. The scan
tool reads serial data from the SDM “Serial Data” line
terminal “24” to the data link connector terminal “9”.
Use Of Special Tools
WARNING: TO AV O I D D E P L O Y M E N T W H E N
TROUBLESHOOTING THE SRS, DO NOT USE
ELECTRICAL TEST EQUIPMENT SUCH AS A
BATTERY–POWERED OR AC–POWERED
VOLTMETER, OHMMETER, ETC, OR ANY TYPE OF
ELECTRICAL EQUIPMENT OTHER THAN THAT
SPECIFIED IN THIS MANUAL. DO NOT USE A NON
POWERED PROBE–TYPE TESTER. INSTRUCTIONS
IN THIS MANUAL MUST BE FOLLOWED
CAREFULLY, OTHERWISE PERSONAL INJURY MAY
RESULT. YOU SHOULD BE FAMILIAR WITH THE
TOOLS LISTED IN THIS SECTION UNDER THE
HANDLING SRS SPECIAL TOOLS.
You should be able to measure voltage and resistance.
You should be familiar with proper use of a scan tool such
as the Tech 2 Diagnostic Computer, SRS
Driver/Passenger Load Tool 5–8840–2421–0, Connector
Test Adapter Kit 5–8840–0385–0, and the DVM (Digital
Multimeter) 5–8840–0285–0.
SUPPLEMENTAL RESTRAINT SYSTEM9J–21
THROUGHOUT THIS ENTIRE DEPLOYMENT AND
DISPOSAL PROCEDURE.
9. Twist together one connector wire lead to one
deployment wire. The connection should be
mechanically secure.
10. Bend twisted connection made in the previous step
flat and wrap tightly with electrical tape to insulate and
secure.
11. Twist together, bend and tape the remaining
connector wire lead to the remaining deployment
wire.
12. Connect the deployment harness to the driver air bag
assembly, yellow 2–pin connector at the base of the
steering column. Route deployment harness out the
driver side of the vehicle.
WARNING: DEPLOYMENT WIRES SHALL REMAIN
SHORTED AND NOT BE CONNECTED TO A POWER
SOURCE UNTIL THE AIR BAG IS TO BE DEPLOYED.
THE AIR BAG ASSEMBLY WILL IMMEDIATELY
DEPLOY THE AIR BAG WHEN A POWER SOURCE IS
CONNECTED TO IT.
CONNECTING THE DEPLOYMENT WIRES TO THE
POWER SOURCE SHOULD ALWAYS BE THE FINAL
STEP IN THE AIR BAG ASSEMBLY DEPLOYMENT
PROCEDURE.
FAILURE TO FOLLOW PROCEDURES IN THE
ORDER LISTED COULD RESULT IN PERSONAL
INJURY.
13. Disconnect passenger air bag assembly, yellow 2–pin
connector located behind glove box assembly.
14. Cut the passenger air bag assembly harness
connector from the vehicle leaving at least 15 cm (six
inches) of wire at the connector.
15. Strip 13 mm (1/2 inch) of insulation from blue–white
and pink–blue wire lead of the connector.
16. Cut two 900 cm (30 feet) deployment wires from 0.8
mm
(18 gauge) or thicker multi–strand wire. These
wires will be used to fabricate the passenger
deployment harness.
17. Strip 13 mm (1/2 inch) of insulation from both ends of
the wires cut in the previous step.
18. Short the wires by twisting together one end from
each. Deployment wires shall remain shorted and not
be connected to a power source until the air bag is to
be deployed.
WARNING: FAILURE TO FOLLOW PROCEDURES IN
THE ORDER LISTED COULD RESULT IN PERSONAL
INJURY. NEVER CONNECT DEPLOYMENT WIRES
TO ANY POWER SOURCE BEFORE CONNECTING
DEPLOYMENT WIRES TO THE AIR BAG ASSEMBLY
LEADS. DEPLOYMENT WIRES SHALL REMAIN
SHORTED AND NOT BE CONNECTED TO A POWER
SOURCE UNTIL THE AIR BAG IS TO BE DEPLOYED.
THE AIR BAG ASSEMBLY WILL IMMEDIATELY
DEPLOY THE AIR BAG WHEN A POWER SOURCE IS
CONNECTED TO IT. WEAR SAFETY GLASSES
THROUGHOUT THIS ENTIRE DEPLOYMENT AND
DISPOSAL PROCEDURE.19. Twist together one connector wire lead to one
deployment wire. The connection should be
mechanically secure.
20. Bend twisted connection made in the previous step
flat and wrap tightly with electrical tape to insulate and
secure.
21. Twist together, bend and tape the remaining
connector wire lead to the remaining deployment
wire.
22. Connect the deployment harness to the passenger air
bag assembly, yellow 2–pin connector located behind
the glove box assembly. Route deployment harness
out the passenger side of the vehicle.
WARNING: DEPLOYMENT WIRES SHALL REMAIN
SHORTED AND NOT BE CONNECTED TO A POWER
SOURCE UNTIL THE AIR BAG IS TO BE DEPLOYED.
THE AIR BAG ASSEMBLY WILL IMMEDIATELY
DEPLOY THE AIR BAG WHEN A POWER SOURCE IS
CONNECTED TO IT. CONNECTING THE
DEPLOYMENT WIRES SHOULD ALWAYS BE THE
FINAL STEP IN THE AIR BAG ASSEMBLY
DEPLOYMENT PROCEDURE. FAILURE TO FOLLOW
PROCEDURES IN THE ORDER LISTED COULD
RESULT IN PERSONAL INJURY.
23. Verify that the inside of the vehicle and the area
surrounding the vehicle are clear of all people and
loose or flammable objects.
24. Stretch the driver and passenger deployment
harness to their full length.
25. Completely cover windshield area and front door
window openings with a drop cloth, blanket or similar
item. This reduces the possibility of injury due to
possible fragmentation of the vehicle’s glass or
interior.
26. Notify all people in the immediate area that you intend
to deploy the air bags. The deployment will be
accompanied by a substantial noise which may
startle the uninformed.
27. Separate the two ends of the driver deployment
harness wires.
WARNING: DEPLOYMENT WIRES SHALL REMAIN
SHORTED AND NOT BE CONNECTED TO A POWER
SOURCE UNTIL THE AIR BAG IS TO A POWER
SOURCE UNTIL THE AIR BAG IS TO BE DEPLOYED.
THE AIR BAG ASSEMBLY WILL IMMEDIATELY
DEPLOY THE AIR BAG WHEN A POWER SOURCE IS
CONNECTED TO IT. CONNECTING THE
DEPLOYMENT WIRES TO THE POWER SOURCE
SHOULD ALWAYS BE THE FINAL STEP IN THE AIR
BAG ASSEMBLY DEPLOYMENT PROCEDURE.
FAILURE TO FOLLOW PROCEDURES IN THE
ORDER LISTED COULD RESULT IN PERSONAL
INJURY.
NOTE: When the air bag deploys, the rapid gas
expansion will create a substantial noise. Notify all
people in the immediate area that you intend to deploy the
air bags.