Dodge Ram Truck 1500-2500-3500. Manual - part 555

1. Begin the cleanup by using a vacuum cleaner to

remove any residual powder from the vehicle inte-
rior. Clean from outside the vehicle and work your
way inside, so that you avoid kneeling or sitting on
a non-cleaned area.

2. Be certain to vacuum the heater and air condition-

ing outlets as well. Run the heater and air condi-
tioner blower on the lowest speed setting and
vacuum any powder expelled from the outlets.

CAUTION: Deployed front airbags having two initi-
ators (squibs) in the airbag inflator may or may
not have live pyrotechnic material within the infla-
tor. Do not dispose of these airbags unless you
are sure of complete deployment. Refer to AIRBAG
SQUIB STATUS . All damaged, faulty, or non-de-
ployed supplemental restraints which are replaced on vehicles are to be handled and disposed of properly.
If an airbag or seat belt tensioner unit is faulty or damaged and non-deployed, refer to the Hazardous Sub-
stance Control System for proper disposal. Be certain to dispose of all non-deployed and deployed supple-
mental restraints in a manner consistent with state, provincial, local and federal regulations.

3. Next, remove the deployed supplemental restraints from the vehicle. Refer to the appropriate service removal

procedures.

4. You may need to vacuum the interior of the vehicle a second time to recover all of the powder.

SUPPLEMENTAL RESTRAINTS VERIFICATION TEST

NOTE: The following procedure should be performed using a diagnostic scan tool to verify proper supple-
mental restraint system operation following the service or replacement of any supplemental restraint sys-
tem component.

WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, seat belt tensioner, impact
sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative
(ground) cable, then wait two minutes for the system capacitor to discharge before performing further diag-
nosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the
proper precautions could result in accidental airbag deployment.

1. During the following test, the battery negative cable

remains disconnected and isolated, as it was dur-
ing the supplemental restraint system component
removal and installation procedures.

2. Be certain that the diagnostic scan tool contains

the latest version of the proper diagnostic software.
Connect the scan tool to the 16-way Data Link
Connector (DLC) (1). The DLC is located on the
driver side lower edge of the instrument panel (2),
outboard of the steering column.

3. Turn the ignition switch to the On position and exit

the vehicle with the scan tool.

4. Check to be certain that nobody is in the vehicle,

then reconnect the battery negative cable.

5. Using the scan tool, read and record the active

(current) Diagnostic Trouble Code (DTC) data.

6. Next, use the scan tool to read and record any

stored (historical) DTC data.

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7. If any DTC is found in Step 5 or Step 6, refer to the appropriate diagnostic information.

8. Use the scan tool to erase the stored DTC data. If any problems remain, the stored DTC data will not erase.

Refer to the appropriate diagnostic information to diagnose any stored DTC that will not erase. If the stored DTC
information is successfully erased, go to Step 9.

9. Turn the ignition switch to the Off position for about fifteen seconds, and then back to the On position. Observe

the airbag indicator in the instrument cluster. It should illuminate for six to eight seconds, and then go out. This
indicates that the supplemental restraint system is functioning normally and that the repairs are complete. If the
airbag indicator fails to light, or lights and stays on, there is still an active supplemental restraint system fault or
malfunction. Refer to the appropriate diagnostic information to diagnose the problem.

MODULE-OCCUPANT RESTRAINT CONTROLLER

DESCRIPTION

The Airbag Control Module (ACM) (1) is also some-
times referred to as the Occupant Restraint Controller
(ORC). The ACM is located below the instrument
panel center stack in the passenger compartment of
the vehicle, where it is secured by three screws to a
stamped steel mounting bracket welded onto the top
of the floor panel transmission tunnel just forward of
the instrument panel center support bracket. Con-
cealed within a hollow in the center of the die cast alu-
minum ACM housing is the electronic circuitry of the
ACM which includes a microprocessor, an electronic
impact sensor, an electronic safing sensor, and an
energy storage capacitor. A stamped metal cover plate
is secured to the bottom of the ACM housing with four
screws to enclose and protect the internal electronic
circuitry and components.

An arrow (2) printed on the label (3) on the top of the ACM housing provides a visual verification of the proper
orientation of the unit, and should always be pointed toward the front of the vehicle. The ACM housing has integral
mounting flanges on three corners. The mounting flange to the left of the connector receptacle has an integral locat-
ing pin on its lower surface. Both left side flanges have round mounting holes, while the flange on the right side has
a slotted mounting hole. A molded plastic electrical connector (4) with two receptacles, one containing twenty-four
terminal pins and the other containing thirty-two terminal pins, exits the rearward facing side of the ACM housing.
These terminal pins connect the ACM to the vehicle electrical system through two dedicated take outs and connec-
tors of the instrument panel wire harness.

The impact sensor and safing sensor internal to the ACM are calibrated for the specific vehicle, and are only ser-
viced as a unit with the ACM. In addition, there are unique versions of the ACM for light and heavy-duty models,
and for vehicles with or without the optional side curtain airbags. The ACM cannot be repaired or adjusted and, if
damaged or faulty, it must be replaced.

OPERATION

The microprocessor in the Airbag Control Module (ACM) contains the supplemental restraint system logic circuits
and controls all of the supplemental restraint system components. The ACM uses On-Board Diagnostics (OBD) and
can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the
Programmable Communications Interface (PCI) data bus network. This method of communication is used for control
of the airbag indicator in the ElectroMechanical Instrument Cluster (EMIC) and for supplemental restraint system
diagnosis and testing through the 16-way data link connector located on the driver side lower edge of the instrument
panel. (Refer to 8 - ELECTRICAL/INSTRUMENT CLUSTER/AIRBAG INDICATOR - OPERATION).

The ACM microprocessor continuously monitors all of the supplemental restraint system electrical circuits to deter-
mine the system readiness. If the ACM detects a monitored system fault, it sets an active and stored Diagnostic

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Trouble Code (DTC) and sends electronic messages to the EMIC over the PCI data bus to turn on the airbag indi-
cator. An active fault only remains for the duration of the fault, or in some cases for the duration of the current
ignition switch cycle, while a stored fault causes a DTC to be stored in memory by the ACM. For some DTCs, if a
fault does not recur for a number of ignition cycles, the ACM will automatically erase the stored DTC. For other
internal faults, the stored DTC is latched forever.

In standard cab models, the ACM also monitors 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. 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 circuits; a fused ignition switch output (run) circuit through a fuse in
the Integrated Power Module (IPM), and a fused ignition switch output (run-start) circuit through a second fuse in
the IPM. The ACM receives ground through a ground circuit and take out of the instrument panel wire harness. This
take out has a single eyelet terminal connector that is secured by a ground screw to the instrument panel structural
support. These connections allow the ACM to be 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 supplemental restraint compo-
nents for up to one second following a battery disconnect or failure. The purpose of the capacitor is to provide
backup supplemental restraint system protection in case there is a loss of battery current supply to the ACM during
an impact.

Two sensors are contained within the ACM, an electronic impact sensor and a safing sensor. The electronic impact
sensors are accelerometers that sense the rate of vehicle deceleration, which provide verification of the direction
and severity of an impact. On models equipped with optional side curtain airbags, the ACM also monitors inputs
from two remote side impact sensors located within both the left and right B-pillars to control deployment of the side
curtain airbag units.

The safing sensor is an electronic accelerometer sensor within the ACM that provides an additional logic input to the
ACM microprocessor. The safing sensor is used to verify the need for a supplemental restraint deployment by
detecting impact energy of a lesser magnitude than that of the primary electronic impact sensors, and must exceed
a safing threshold in order for the airbags to deploy. Vehicles equipped with optional side curtain airbags feature a
second safing sensor within the ACM to provide confirmation to the ACM microprocessor of side impact forces. This
second safing sensor is a bi-directional unit that detects impact forces from either side of the vehicle.

Pre-programmed decision algorithms in the ACM microprocessor determine when the deceleration rate as signaled
by the impact sensors and the safing sensors indicate an impact that is severe enough to require supplemental
restraint system protection and, based upon the severity of the monitored impact and the status of the passenger
airbag on/off switch input, determines the level of front airbag deployment force required for each front seating posi-
tion. When the programmed conditions are met, the ACM sends the proper electrical signals to deploy the dual
multistage front airbags at the programmed force levels, the front seat belt tensioners and, if the vehicle is so
equipped, either side curtain airbag unit. For vehicles equipped with the passenger airbag on/off switch, the pas-
senger front airbag and seat belt tensioner will be deployed by the ACM only if enabled by the switch (passenger
airbag on/off switch indicator Off) at the time of the impact.

The hard wired inputs and outputs for the ACM may be diagnosed and tested using conventional diagnostic tools
and methods. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ACM, the
PCI data bus network, or the electronic message inputs to and outputs from the ACM. The most reliable, efficient,
and accurate means to diagnose the ACM, the PCI data bus, and the electronic message inputs to and outputs from
the ACM requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

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REMOVAL

MODULE

WARNING: To avoid personal injury or death, never strike or drop the airbag control module, as it can dam-
age the impact sensor or affect its calibration. The airbag control module contains the impact sensor, which
enables the system to deploy the supplemental restraints. If an airbag control module is accidentally
dropped during service, the module must be scrapped and replaced with a new unit. Failure to observe this
warning could result in accidental, incomplete, or improper supplemental restraint deployment.

1. Disconnect and isolate the battery negative cable.

Wait two minutes for the system capacitor to dis-
charge before further service.

2. On models with a manual transmission, remove the

floor console from the top of the floor panel trans-
mission tunnel. (Refer to 23 - BODY/INTERIOR/
FLOOR CONSOLE - REMOVAL).

3. On models with an automatic transmission, remove

the ACM cover from the instrument panel. (Refer to
8 - ELECTRICAL/RESTRAINTS/ACM COVER -
REMOVAL).

4. Reach through the rearward facing opening below

the instrument panel center stack support bracket
on the top of the floor panel transmission tunnel to
access and disconnect the two wire harness con-
nectors (3 & 4) for the Airbag Control Module
(ACM) (1) from the ACM connector receptacles located on the rearward facing side of the module. To disconnect
the wire harness connectors from the ACM, depress the release tab and lift the lever arm on each connector.

5. From the left side of the floor panel transmission tunnel, reach behind the module to access and loosen the

screw (2) that secures the right side of the ACM to the bracket (5) on the floor panel transmission tunnel. Loosen
the screw about 7 millimeters (0.25 inch).

6. From the left side of the floor panel transmission tunnel, remove the two screws that secure the left side of the

ACM to the bracket on the floor panel transmission tunnel.

7. Still working from the left side of the floor panel transmission tunnel, lift the ACM upward far enough to disen-

gage the locating pin on the bottom of the ACM mounting flange from the locating hole in the mounting bracket,
then slide the ACM toward the left far enough to disengage the slotted hole in the right ACM mounting flange
from under the head of the previously loosened right mounting screw.

8. Remove the ACM from the left side of the floor panel transmission tunnel.

COVER

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