Express 3/4 Ton Van V8-4.8L VIN V (2003)
Seat Sensor/Switch: Description and Operation
INFLATABLE RESTRAINT SEAT POSITION SWITCH
The seat position switch (SPS) is used to determine the proximity of a front driver or passenger seat position with respect to the frontal air bag. The SPS
interfaces with the SDM. The state of the SPS allows the SDM to disable stage 2 of the frontal air bag for a front seat that is forward of a
forward/rearward point in seat track travel. The SPS is a Hall effect sensor that is mounted on the seat track of both the driver and passenger seats. The
seat track includes a metal bracket that shunts the SPS magnetic circuit creating two states of seat position. The shunted state represents a rearward seat
position. The non-shunted state represents a forward position. The SPS provides two current ranges, one range for the shunted state and a second range
for a non-shunted state. These two states are inputs to the sensing and diagnostic module (SDM). State 1 (shunted) being the rearward threshold and state
2 (non-shunted) being the forward threshold. When the SDM receives input from a SPS that state 1 threshold is reached (seat is rearward) the SDM will
not disable stage 2 deployment, if required by the deployment sensors. When state 2 threshold is reached (seat is forward) the SDM will disable stage 2
deployment on the side the seat is forward. The SDM monitors the SPS circuit and if a fault is detected the SDM will set codes B0083 or B0084 and
defaults to disabling stage 2 frontal deployment. This will only default on the side of the vehicle the sensor has a fault. It's important to understand that
the SPS is secondary to the manual I/P module disable switch. If the I/P module disable switch is in the disable mode the passenger air bag will not
deploy regardless of the SPS status.
