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SUPPLEMENTARY RESTRAINT SYSTEM (SRS)
9
11.1.6.2. RESTRAINT WITH AIRBAGS
11.1.6.2.1. ECU
The SRS ECU
gets power supply from vehicle
battery
and
is designed to perform the following
functions in the air bag system:
FUNCTIONS
ENERGY RESERVE
SRS ECU
maintains a Reserve energy supply to
provide deployment energy after ignition voltage is
lost only during crash. However, the energy
reserve is for a limited and short duration,
therefore battery terminals and its connection to
airbag ECU needs to be checked.
CRASH DETECTION
SRS ECU
monitors vehicle deceleration levels to
detect crashes which are severe enough to
warrant deployment.
AIR BAG DEPLOYMENT
When sensors detect a frontal crash of sufficient
severity, and send signals to the SRS ECU which
in turn take deployment decision and causes
enough current to flow to the air bag (inflator)
modules to deploy them.
LAMP CONTROL AFTER FIRST CRASH:
“AIR BAG” warning lamp is turned and kept ON.
Reset this memory mode using diagnostic tester.
ECU needs replacement if it has sensed a crash.
Once Airbag firing signal is given, ECU cannot be
reset using diagnostic tester.
MALFUNCTION DETECTION
The SRS ECU performs diagnostic monitoring of
the air bag system electrical components and
switches on the indication on instrument cluster
and sets a diagnostic trouble code when a
malfunction is detected.
MALFUNCTION DIAGNOSIS
SRS ECU
displays air bag diagnostic trouble
codes and system status information through the
use of diagnostic tool.
“AIR BAG” WARNING LAMP
A warning indicator in instrument cluster will alert
for any malfunction of the airbag “SRS”. Under
normal/ fault free condition, the air bag warning
light comes “ON” for approximately 3 seconds and
goes “OFF” when ignition is turned ON.
LOCATION
Airbag ECU is mounted on the floor tunnel along
the centre line of the vehicle under the floor
console.