2002 DODGE RAM change key battery

POWERTRAIN CONTROL
MODULE
DESCRIPTION
DESCRIPTION - PCM
The Powertrain Control Module (PCM) is located
in the engine compartment (Fig. 17). The PCM is
referred to as JTEC.
DESCRIPTION - MODES OF OPERATION
As input signals to the Powertrain Control Module
(PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate
different injector pulse width and ignition timing for
idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input
signals and responds only according to preset PCM
programming. Input from the oxygen (O2S) sensors
is not monitored during Open Loop modes.
During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
²Ignition switch ON²Engine start-up (crank)
²Engine warm-up
²Idle
²Cruise
²Acceleration
²Deceleration
²Wide open throttle (WOT)
²Ignition switch OFF
The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle
and cruise modes, (with the engine at operating tem-
perature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following
actions occur:
²The PCM pre-positions the idle air control (IAC)
motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant tempera-
ture sensor input. The PCM modifies fuel strategy
based on this input.
²Intake manifold air temperature sensor input is
monitored.
²Throttle position sensor (TPS) is monitored.
²The auto shutdown (ASD) relay is energized by
the PCM for approximately three seconds.
²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the ASD relay. The O2S sensor input is not used by
the PCM to calibrate air-fuel ratio during this mode
of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Starter motor relay
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.
Fig. 17 PCM Location
1 - PCM MOUNTING BOLTS (3)
2 - POWERTRAIN CONTROL MODULE (PCM)
3 - (3) 32±WAY CONNECTORS
BR/BEELECTRONIC CONTROL MODULES 8E - 15

INSTALLATION
WARNING: DISABLE THE AIRBAG SYSTEM
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: WHEN REMOVING A DEPLOYED AIR-
BAG, RUBBER GLOVES, EYE PROTECTION, AND A
LONG-SLEEVED SHIRT SHOULD BE WORN. THERE
MAY BE DEPOSITS ON THE AIRBAG UNIT AND
OTHER INTERIOR SURFACES. IN LARGE DOSES,
THESE DEPOSITS MAY CAUSE IRRITATION TO THE
SKIN AND EYES.
WARNING: USE EXTREME CARE TO PREVENT ANY
FOREIGN MATERIAL FROM ENTERING THE PAS-
SENGER AIRBAG, OR BECOMING ENTRAPPED
BETWEEN THE PASSENGER AIRBAG CUSHION
AND THE PASSENGER AIRBAG DOOR. FAILURE TO
OBSERVE THIS WARNING COULD RESULT IN
OCCUPANT INJURIES UPON AIRBAG DEPLOY-
MENT.
WARNING: THE PASSENGER AIRBAG DOOR MUST
NEVER BE PAINTED. REPLACEMENT PASSENGER
AIRBAG DOORS ARE SERVICED IN THE ORIGINAL
COLORS. PAINT MAY CHANGE THE WAY IN WHICH
THE MATERIAL OF THE AIRBAG DOOR RESPONDS
TO AN AIRBAG DEPLOYMENT. FAILURE TO
OBSERVE THIS WARNING COULD RESULT IN
OCCUPANT INJURIES UPON AIRBAG DEPLOY-
MENT.
(1) Carefully inspect the five receptacle slots
around the top and sides of the passenger airbag
door opening of the instrument panel top cover.
Remove any of the small metal airbag door snap
retainers that did not remain on the molded airbag
door tabs during the removal procedure.
(2) If the removed passenger airbag module is
being reinstalled, install the metal snap retainers
recovered in Step 1onto the proper airbag door tabs.
Each of the five molded airbag door tabs must have a
snap retainer on it before it is installed in the instru-ment panel. New replacement passenger airbags
come with new airbag door snap retainers installed.
(3) Carefully position the passenger airbag onto
the instrument panel.
(4) Align the five tabs and retainers on the upper
edge and sides of the passenger airbag door with the
receptacles in the instrument panel top cover.
(5) Using hand pressure, press firmly on the pas-
senger airbag door over each of the tab and retainer
locations until each of them is fully engaged in its
receptacle. Be certain that each of the metal snap
retainers is in position on the airbag door tabs.
(6) Install and tighten the five screws that secure
the passenger airbag front and rear mounting brack-
ets to the instrument panel (Fig. 18). Tighten the
screws to 9 N´m (80 in. lbs.).
(7) Install and tighten the four screws that secure
the two plastic support brackets of the passenger air-
bag door panel outlet housing to the glove box open-
ing upper reinforcement. Tighten the screws to 2.2
N´m (20 in. lbs.).
(8) Reach through and above the glove box opening
to access and reconnect the passenger airbag pigtail
wire connector to the instrument panel wire harness
connector (Fig. 17). Be certain that the passenger air-
bag pigtail wire connector is fully engaged with and
latched to the instrument panel wire harness connec-
tor.
(9) Reinstall the glove box opening upper trim onto
the instrument panel. (Refer to 23 - BODY/INSTRU-
MENT PANEL/GLOVE BOX OPENING UPPER
TRIM - INSTALLATION).
(10) Reinstall the glove box onto the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
GLOVE BOX - INSTALLATION).
(11) Do not reconnect the battery negative cable at
this time. The airbag system verification test proce-
dure should be performed following service of any
airbag system component. (Refer to 8 - ELECTRI-
CAL/RESTRAINTS - STANDARD PROCEDURE -
VERIFICATION TEST).
PASSENGER AIRBAG ON/OFF
SWITCH
DESCRIPTION
The passenger airbag on-off switch is standard
equipment on this model when it is not equipped
with a full size rear seat. This switch is a single pole,
single throw switch with a single integral red Light-
Emitting Diode (LED), and a non-coded key cylinder-
type actuator. The switch is located in the upper
right corner of instrument panel cluster bezel, near
the center of instrument panel to make the Off indi-
cator visible to all front seat occupants. When the
BR/BERESTRAINTS 8O - 23
PASSENGER AIRBAG (Continued)

switch is in its installed position, the only compo-
nents visible through the dedicated opening of the
cluster bezel are the switch face plate and nomencla-
ture, the key cylinder actuator, and a small round
lens with the text9Off9imprinted on it. The ªOnº
position of the switch is designated by text imprinted
upon the face plate of the switch, but is not illumi-
nated. The remainder of the switch is concealed
behind the switch face plate and the instrument
panel cluster bezel.
The passenger airbag on-off switch housing is con-
structed of molded plastic and has three integral
mounting tabs. These mounting tabs are used to
secure the switch to the back of the molded plastic
switch face plate with three small screws. The
molded plastic face plate also has three integral
mounting tabs that are used to secure the switch and
face plate unit to the instrument panel carrier with
three additional screws. Two short pigtail wires with
molded plastic connector insulators exit the back of
the switch housing and connect the switch to the
vehicle electrical system through two dedicated take
outs of the instrument panel wire harness. The har-
ness take outs are equipped with molded plastic con-
nector insulators that are keyed and latched to
ensure proper and secure switch electrical connec-
tions. The passenger airbag on/off switch cannot be
adjusted or repaired and, if faulty or damaged, the
switch must be replaced.
OPERATION
The passenger airbag on/off switch allows the cus-
tomer to turn the passenger airbag function On or
Off to accommodate certain uses of the right front
seating position where airbag protection may not be
desired. See the owner's manual in the vehicle glove
box for specific recommendations on when to enable
or disable the passenger airbag. The Off indicator of
the switch will be illuminated whenever the switch is
turned to the Off position. The ignition key is the
only key or object that should ever be inserted into
the switch. The on/off switch requires only a partial
key insertion to fully depress a spring-loaded locking
plunger. The spring-loaded locking plunger prevents
the user from leaving the key in the switch. The key
will be automatically ejected when force is not
applied. To actuate the passenger side airbag on/off
switch, insert the ignition key into the switch key
actuator far enough to fully depress the plunger and
rotate to the desired switch position. When the
switch key actuator is rotated to its clockwise stop
(the key actuator slot will be aligned with the Off
indicator lamp), the Off indicator is illuminated and
the passenger airbag is disabled. When the switch is
rotated to its counterclockwise stop (the key actuator
slot will be in a vertical position), the Off indicatorwill be extinguished and the passenger airbag is
enabled.
The passenger airbag on/off switch is connected in
series between the Airbag Control Module (ACM) and
the passenger airbag inflator unit. When the switch
is in the On position, the switch connects the ACM
directly to the passenger airbag inflator. When the
switch is in the Off position it interrupts the inflator
circuits, but replaces the normal resistance in these
circuits with an internal resistor. Thus, the ACM is
unable to distinguish the mode of the switch and still
sends an electrical signal as though it were deploying
the passenger airbag when it detects a sufficient
impact. However, the switch position should not be
changed while the ignition switch is in the On posi-
tion, as the ACM may detect a fault, record a Diag-
nostic Trouble Code (DTC), and illuminate the Airbag
indicator in response to a momentary open it senses
in the passenger airbag inflator circuits as the on/off
switch changes states.
REMOVAL
WARNING: DISABLE THE AIRBAG SYSTEM
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.
(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) Remove the cluster bezel from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
CLUSTER BEZEL - REMOVAL).
(3) Remove the glove box from the instrument
panel. (Refer to 23 - BODY/INSTRUMENT PANEL/
GLOVE BOX - REMOVAL).
(4) Reach through the glove box opening to access
and disconnect the two passenger airbag on/off
switch pigtail wire harness connectors from the
instrument panel wire harness connectors. These
connectors are retained on a bracket located on the
inboard glove box opening reinforcement (Fig. 20).
(5) Remove the three screws that secure the pas-
senger airbag on/off switch face plate to the instru-
ment panel (Fig. 21).
8O - 24 RESTRAINTSBR/BE
PASSENGER AIRBAG ON/OFF SWITCH (Continued)

CAUTION: Before tightening sensor mounting bolt,
be sure sensor is completely flush to cylinder block
(Fig. 28). If sensor is not flush, damage to sensor
mounting tang may result.
(3) Install mounting bolt and tighten to 8 N´m (70
in. lbs.) torque.
(4) Connect sensor pigtail harness to main engine
wiring harness
(5) Install new plastic tie strap (Fig. 27) to secure
sensor pigtail harness to side of engine block. Thread
tie strap through casting hole on cylinder block.
FUEL PUMP RELAY
DESCRIPTION
The 5±pin, 12±volt, fuel pump relay is located in
the Power Distribution Center (PDC). Refer to the
label on the PDC cover for relay location.
OPERATION
The Powertrain Control Module (PCM) energizes
the electric fuel pump through the fuel pump relay.
The fuel pump relay is energized by first applying
battery voltage to it when the ignition key is turned
ON, and then applying a ground signal to the relay
from the PCM.
Whenever the ignition key is turned ON, the elec-
tric fuel pump will operate. But, the PCM will shut-
down the ground circuit to the fuel pump relay in
approximately 1±3 seconds unless the engine is oper-
ating or the starter motor is engaged.
REMOVAL
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 30). Refer to label on PDC
cover for relay location.
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 30) . Refer to label on PDC
cover for relay location.
(1) Install relay to PDC.
(2) Install cover to PDC.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into a
passage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.
The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply elec-
trical current to the motor windings to operate the
stepper motor in one direction. The other 2 wires are
also for 12 volts and ground to supply electrical cur-
rent to operate the stepper motor in the opposite
direction.
Fig. 30 Power Distribution Center (PDC)
1 - POWER DISTRIBUTION CENTER (PDC)
14 - 40 FUEL INJECTION - GASOLINEBR/BE
CRANKSHAFT POSITION SENSOR (Continued)

(M)Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was recorded
(depending if required by CARB and/or EPA). MIL is displayed as an engine icon on instrument panel.
(G)Generator lamp illuminated
Generic Scan
Tool P-CodeDRB Scan Tool Display Brief Description of DTC
P1496 5 Volt Supply, Output Too Low 5 volt sensor feed is sensed to be below an acceptable limit.
( less than 4v for 4 sec )
P1498 High Speed Rad Fan Ground CTRL
Rly CircuitAn open or shorted condition detected in the control circuit of
the #3 high speed radiator fan control relay.
P1499 Hydraulic cooling fan solenoid circuit An open or shorted condition detected in the cooling fan
control solenoid circuit.
P1594 (G) Charging System Voltage Too High Battery voltage sense input above target charging voltage
during engine operation.
P1594 Charging System Voltage Too High Battery voltage sense input above target charging voltage
during engine operation.
P1595 Speed Control Solenoid Circuits An open or shorted condition detected in either of the speed
control vacuum or vent solenoid control circuits.
P1595 Speed Control Solenoid Circuits An open or shorted condition detected in the speed control
vacuum or vent solenoid circuits.
P1596 Speed Control Switch Always High Speed control switch input above maximum acceptable
voltage.
P1597 Speed Control Switch Always Low Speed control switch input below minimum acceptable
voltage.
P1597 Speed Control Switch Always Low Speed control switch input below the minimum acceptable
voltage.
P1598 A/C Pressure Sensor Volts Too High A/C pressure sensor input above maximum acceptable
voltage.
P1598 A/C Sensor Input Hi Problem detected in air conditioning electrical circuit.
P1599 A/C Pressure Sensor Volts Too Low A/C pressure sensor input below minimum acceptable
voltage.
P1599 A/C Sensor Input Lo Problem detected in air conditioning electrical circuit.
P1602 PCM not programmed
P1680 Clutch Released Switch Circuit Problem detected in clutch switch electrical circuit.
P1681 No I/P Cluster CCD/J1850 Messages
ReceivedNo CCD/J1850 messages received from the cluster control
module.
P1682 (G) Charging System Voltage Too Low Battery voltage sense input below target charging voltage
during engine operation and no significant change in voltage
detected during active test of generator output circuit.
P1682 Charging System Voltage Too Low Charging system output voltage low.
P1683 SPD CTRL PWR Relay; or S/C 12v
Driver CKTAn open or shorted condition detected in the speed control
servo power control circuit.
P1683 Spd ctrl pwr rly, or s/c 12v driver circuit An open or shorted condition detected in the speed control
servo power control circuit.
P1684 Batt Loss (disconnected) in last 50
StartsThe battery has been disconnected within the last 50 starts
P1685 SKIM Invalid Key - (Wrong or Invalid
Key MSG Received From SKIM)The engine controler has received an invalid key from the
SKIM.
25 - 14 EMISSIONS CONTROLBR/BE
EMISSIONS CONTROL (Continued)