Suzuki XL7 2007 Service Manual page 2015

Inflatable Restraint Sensing and Diagnostic
Module (SDM)
The sensing and diagnostic module (SDM) is a
microprocessor and the control center for the
supplemental inflatable restraint (SIR) system. The SDM
contains internal sensors along with several external
sensors, if equipped, mounted at strategic locations on
the vehicle. In the event of a collision, the SDM
compares the signals from the internal and external
sensors to a value stored in memory. When the
generated signals exceed the stored value, the SDM will
cause current to flow through the appropriate
deployment loops to deploy the air bags. The SDM
records the SIR system status when a deployment
occurs and turns the AIR BAG indicator located in the
IPC ON. The SDM performs continuous diagnostic
monitoring of the SIR system electrical components and
circuitry when the ignition is turned ON. If the SDM
detects a malfunction, a DTC will be stored and the SDM
will command the AIR BAG indicator ON, notifying the
driver that a malfunction exist. In the event that ignition
positive voltage is lost during a collision, the SDM
maintains a 23-volt loop reserve (23 VLR) for
deployment of the air bags. It is important when
disabling the SIR system for servicing or rescue
operations to allow the 23 VLR to dissipate, which could
take up to 1 minute.
Inflatable Restraint Passenger Presence
System
NOTE
The passenger presence system (PPS),
heated seat element (if equipped), and the
seat bottom foam cushion is a calibrated unit
and cannot be service separately. After
repairing or replacing the PPS, the system
must be rezeroed in order to function
properly.
The PPS is used to monitor the weight of an occupant on
the front outboard passenger seat and communicate the
status to the sensing and diagnostic module (SDM)
whether to enable or suppress the deployment of the
instrument panel (I/P) inflator module. The PPS consist
of an electronic control module, sensor mat, heated seat
element (if equipped), wiring harness, and PASSENGER
AIR BAG ON/OFF indicators. The sensor is made up of
several flexible conductive metal strips placed
underneath the seat cushion trim. These sensor strips
transmit and receive a low-level electric field. The weight
of the occupant sitting in the front passenger seat is
measured as a change in current flow within the sensor
mat. If the sensor determines that the occupant weight is
less than a specified value, the PPS module will send a
suppress signal to the SDM to disable the I/P module. If
the sensor determines the occupant weight is higher
than a specified value, the PPS module will send an
enable signal to the SDM to enable the I/P. The PPS
module will notify the customer of the enable/disable
status by turning on one of the PASSENGER AIR BAG
ON/OFF indicators located in the center of the
instrument panel cluster (IPC). The PPS monitors itself
for faults and will display flash diagnostic trouble codes
(DTCs) when a fault is detected and the SDM
commands it by using the PASSENGER AIR BAG ON/
OFF indicators. The PPS will also notify the SDM of a
fault and the SDM will request the IPC to turn the AIR
BAG indicator located on the IPC ON. To determine what
DTCs have been set by the PPS, the scan tool is used to
command the SDM to request the PPS to flash the DTCs
using the PASSENGER AIR BAG ON/OFF indicators
located on the I/P.
Inflatable Restraint PASSENGER AIR BAG ON/
OFF indicator
The PASSENGER AIR BAG ON/OFF indicators is used
to notify the driver and passenger when the I/P and the
right front air bag is enable or disable.
AIR BAG Indicator
The AIR BAG indicator, located in the instrument panel
cluster (IPC) is used to notify the driver of SIR system
malfunctions and to verify that the sensing and
diagnostic module (SDM) is communicating with the
IPC. When the ignition is turned ON, the SDM is
supplied with ignition positive voltage. The SDM
requests the IPC to flash the AIR BAG indicator seven
times. While flashing the indicator, the SDM conducts
test on all SIR system components and circuits. If no
malfunctions are detected the SDM will communicate
with the IPC through the class 2 serial data circuit and
command the AIR BAG indicator OFF. The SDM
provides continuous monitoring of the air bag circuits by
conducting a sequence of checks. If a malfunction is
detected the SDM will store a diagnostic trouble code
(DTC) and command the IPC to turn the AIR BAG
indicator ON via class 2 serial data. The presence of a
SIR system malfunction could result in non-deployment
of the air bags or deployment in conditions less severe
than intended. The AIR BAG indicator will remain ON
until the malfunction has been repaired.
Air Bag System: 8B-3