Removal - Jeep Wrangler 2001 Service Manual

TJ
AIRBAG CONTROL MODULE (Continued)
OPERATION). The ACM microprocessor continuously
monitors all of the airbag system electrical circuits to
determine the system readiness. If the ACM detects
a monitored system fault, it sets an active Diagnostic
Trouble Code (DTC) and sends messages to the
EMIC over the PCI data bus to turn on the airbag
indicator. If the airbag system fault is still present
when the ignition switch is turned to the Off posi-
tion, the DTC is stored in memory by the ACM. How-
ever, if a fault does not recur for a number of ignition
cycles, the ACM will automatically erase the stored
DTC.
The ACM also receives a resistor multiplexed input
from the passenger airbag on/off switch and provides
a control output for the Off indicator in the switch
through a passenger airbag indicator driver circuit. If
the passenger airbag on/off switch is set to the Off
position, the ACM turns on the passenger airbag
on/off switch Off indicator and will internally disable
the passenger airbag from being deployed if an
impact is detected that is sufficient for an airbag
deployment. The ACM also turns on the on/off switch
Off indicator for about seven seconds each time the
ignition switch is turned to the On position as a bulb
test. Following the bulb test, the ACM controls the
status of the Off indicator based upon the resistance
of the input from the on/off switch. The ACM will
also set and/or store a DTC for faults it detects in the
passenger airbag on/off switch circuits, and will turn
on the airbag indicator in the EMIC if a fault has
been detected.
The ACM receives battery current through two cir-
cuits, on a fused ignition switch output (run) circuit
through a fuse in the fuse block, and on a fused igni-
tion switch output (run-start) circuit through a sec-
ond fuse in the fuse block. The ACM is grounded
through a ground circuit and take out of the cross
body wire harness. This take out has a single eyelet
terminal connector secured by a ground screw to the
right cowl side inner panel below the instrument
panel in the passenger compartment. Therefore, the
ACM is operational whenever the ignition switch is
in the Start or On positions. The ACM also contains
an energy-storage capacitor. When the ignition
switch is in the Start or On positions, this capacitor
is continually being charged with enough electrical
energy to deploy the airbags for up to one second fol-
lowing a battery disconnect or failure. The purpose of
the capacitor is to provide backup airbag system pro-
tection in case there is a loss of battery current sup-
ply to the ACM during an impact. The capacitor is
only serviced as a unit with the ACM.
Two sensors are contained within the ACM, an
electronic impact sensor and a safing sensor. The
electronic impact sensor is an accelerometer that
senses the rate of vehicle deceleration, which pro-
2001 JEEP WRANGLER
vides verification of the direction and severity of an
impact. A pre-programmed decision algorithm in the
ACM microprocessor determines when the decelera-
tion rate as signaled by the impact sensor indicates
an impact that is severe enough to require airbag
system protection. When the programmed conditions
are met, the ACM sends an electrical signal to deploy
the airbags and, on quad cab models, the seat belt
tensioners. The safing sensor is an electromechanical
sensor within the ACM that is connected in series
between the ACM microprocessor deployment circuit
and the airbags/seat belt tensioners. The safing sen-
sor is a normally open switch that is used to verify or
confirm the need for an airbag deployment by detect-
ing impact energy of a lesser magnitude than that of
the electronic impact sensor, and must be closed in
order for the airbags to deploy. The impact sensor
and safing sensor are calibrated for the specific vehi-
cle, and are only serviced as a unit with the ACM.

REMOVAL

WARNING:
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. DISCON-
NECT AND ISOLATE THE BATTERY NEGATIVE
(GROUND) CABLE, THEN WAIT TWO MINUTES FOR
THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE
BEFORE PERFORMING FURTHER DIAGNOSIS OR
SERVICE. THIS IS THE ONLY SURE WAY TO DIS-
ABLE THE AIRBAG SYSTEM. FAILURE TO TAKE
THE PROPER PRECAUTIONS COULD RESULT IN
ACCIDENTAL AIRBAG DEPLOYMENT AND POSSI-
BLE PERSONAL INJURY.
WARNING: THE AIRBAG CONTROL MODULE CON-
TAINS THE IMPACT SENSOR, WHICH ENABLES
THE SYSTEM TO DEPLOY THE AIRBAGS. NEVER
STRIKE OR KICK THE AIRBAG CONTROL MODULE,
AS IT CAN DAMAGE THE IMPACT SENSOR OR
AFFECT ITS CALIBRATION. IF AN AIRBAG CON-
TROL MODULE IS ACCIDENTALLY DROPPED DUR-
ING SERVICE, THE MODULE MUST BE SCRAPPED
AND REPLACED WITH A NEW UNIT. FAILURE TO
OBSERVE THIS WARNING COULD RESULT IN ACCI-
DENTAL, INCOMPLETE, OR IMPROPER AIRBAG
DEPLOYMENT AND POSSIBLE OCCUPANT INJU-
RIES.
(1) Disconnect and isolate the battery negative
cable. If either of the airbags has not been deployed,
wait two minutes for the system capacitor to dis-
charge before further service.
(2) Pull the carpet on the right and left sides of
the floor panel transmission tunnel rearward far
RESTRAINTS
DISABLE THE AIRBAG
8Os - 7
SYSTEM