Freelander Body Repair Manual — part 19
RESTRAINT SYSTEMS
DESCRIPTION AND OPERATION
5
SRS wiring
Never attempt to modify, splice or repair SRS wiring.
Never install electronic equipment such as a mobile
telephone, two way radio or in car entertainment
system in such a way that it interferes electrically
with the SRS wiring.
Always ensure SRS wiring is routed correctly. Be
careful to avoid trapping or pinching the SRS wiring.
Ensure the are no possible chafing points.
Always use specified earth fixings tightened to the
correct torque. Poor earthing can cause intermittent
problems that are difficult to diagnose.
Ensure all SRS wiring connectors are mated
correctly and securely fastened. Do not leave the
connectors hanging loose.
Warning labels
Warning labels are displayed on SRS parts and
prominent places on the vehicle to indicate:
•
The need for caution when working in close
proximity to SRS parts.
•
That, if a passenger airbag module is installed,
rearward facing child seats are prohibited on
front passenger seats.
•
The publication where suitable reference and
advice can be found (usually the Workshop
Manual or Owner’s Handbook).
RESTRAINT SYSTEMS
6
DESCRIPTION AND OPERATION
System description
The supplementary restraint system (SRS) provides
additional protection for front seat occupants during
a frontal collision above a preset severity.
Impact zone for SRS activation (approximate)
SRS component location
1. SRS warning lamp
2. Passenger’s airbag module (optional)
3. Rotary coupler
4. Driver’s airbag module
5. Airbag ECU
6. Seat belt pretensioners
RESTRAINT SYSTEMS
DESCRIPTION AND OPERATION
7
The SRS is an electronically controlled, single point
sensing system. The system comprises an airbag
Electronic Control Unit (ECU), a driver’s airbag
module, a passenger’s airbag module (optional), two
seat belt pretensioners and a warning lamp.
Interconnecting wiring for the system is contained in
yellow sleeving and integrated into the vehicle
harnesses. A rotary coupler connects the vehicle
harness to the driver’ airbag module. On vehicles
with a passenger’s airbag module, a link lead
connects the module to the vehicle harness. An ISO
9141 K line (bi-directional) serial communication link
connects the airbag ECU to the vehicle’s diagnostic
socket.
The system is operational only while the ignition is
on. With the ignition on, any frontal collision is
detected by the airbag ECU. If the impact is above
the preset severity, the ECU sends out simultaneous
fire signals to the airbag modules and the seat belt
pretensioners. The airbag modules then deploy
protective airbags in front of the driver and front seat
passenger, and the seat belt pretensioners retract to
tighten the front seat belts. Collision detection to full
deployment of the airbags and pretensioners takes
approximately 45 milliseconds.
WARNING: All the SRS parts, including the
wiring harness, link lead (where fitted) and
rotary coupler, must be renewed after the
airbags and pretensioners have deployed.
SRS schematic
1. Ignition power supply
2. Instrument pack
3. Warning lamp
4. Airbag ECU
5. Rotary coupler
6. Driver’s airbag module
7. Passenger’s airbag module
8. Seat belt pretensioners
9. Diagnostic socket
RESTRAINT SYSTEMS
8
DESCRIPTION AND OPERATION
Airbag ECU
The airbag ECU controls the operation of the system
and also contains the collision detection sensors.
The airbag ECU is attached to a bracket on the
transmission tunnel, directly below the heater. A
vehicle earth output connects to one of the fixings. A
30 pin connector provides the airbag ECU
connection with the vehicle harness.
Incorporated into the airbag ECU is a mechanical
safing sensor, an electronic single point sensor and
integrated circuits for control and diagnostics. The
mechanical safing sensor is a normally open switch
that closes at the preset deceleration limit. The
single point sensor is an accelerometer that
produces an output proportional to the vehicle’s
deceleration .
Power back-up
The airbag ECU incorporates capacitors to ensure
the system will function if the external power supply
is disconnected during a collision:
•
A hardware capacitor provides power for 200
milliseconds to enable system operation and
collision recording.
•
Individual capacitors for each fire signal output
provide power for 150 milliseconds.
The capacitors are kept charged while the ignition is
on by a dc-dc voltage converter incorporated into the
airbag ECU. It can take up to 10 minutes from the
ignition being switched off for the energy stored in
the capacitors to fully dissipate and make the
system inert.
Airbag ECU
Airbag ECU pin connections
Pin Description
Pin Description
1. RH pretensioner (+ve)
2. RH pretensioner (-ve)
3. LH pretensioner (+ve)
4. LH pretensioner (-ve)
5. Vehicle supply
6. Vehicle earth
7. SRS warning lamp
8. Not used
9. ISO 9141 K line
10. Driver airbag module (+ve)
11. Driver’s airbag module (-ve)
12. Not used
13. Passenger’s airbag (+ve) - where fitted
14. Passenger’s airbag (-ve) - where fitted
15. to 30. Not used
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст