1998 DODGE RAM 1500 Pcm wiring diagram

(2) Check the heated seat sensor (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
SENSOR - DIAGNOSIS AND TESTING).
(3) Check the heated seat switch (Refer to 8 -
ELECTRICAL/HEATED SEATS/DRIVER HEATED
SEAT SWITCH - DIAGNOSIS AND TESTING).
NOTE: Refer to Wiring for the location of complete
heated seat system wiring diagrams and connector
pin-out information.
(4) Using a voltmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for voltage at the appropriate pin cavities. 12v
should be present. If OK go to Step 5, if Not, Repair
the open or shorted voltage supply circuit as
required.
(5) Using a ohmmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for proper continuity to ground on the ground
pin cavities. Continuity should be present. If OK
replace the heated seat module with a known good
unit and retest system, if Not OK, Repair the open or
shorted ground circuit as required.
REMOVAL
(1) Position the driver seat to the full rearward
and inclined position.
(2) Working under the driver front seat, remove
the two heated seat module retaining screws. Due to
the fact that the retaining screws are installed with
the seat cushion pan removed, a small right angle
screwdriver will be required to access and remove the
screws.
(3) Disconnect the seat wire harness connector
from the connector receptacle on the back of the
heated seat module. Depress the connector retaining
tab and pull straight apart.
(4) Remove the heated seat module from under the
front seat.
INSTALLATION
(1) Position the heated seat module under the
front seat.
(2) Connect the seat wire harness connector on the
connector receptacle on the back of the heated seat
module.
(3) Working under the driver front seat, install the
heated seat module retaining screws.
(4) Re-position the driver seat.
POWERTRAIN CONTROL
MODULE
DESCRIPTION
DESCRIPTION - PCM
The Powertrain Control Module (PCM) is located
in the right-rear section of the engine compartment
under the cowl (Fig. 4).
Two different PCM's are used (JTEC and
NGC). These can be easily identified. JTEC's
use three 32±way connectors, NGC's use four
38±way connectors
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.
Fig. 4 POWERTRAIN CONTROL MODULE (PCM)
LOCATION
1 - COWL GRILL
2 - PCM
3 - COWL (RIGHT-REAR)
DRELECTRONIC CONTROL MODULES 8E - 7
HEATED SEAT MODULE (Continued)

CHARGING
TABLE OF CONTENTS
page page
CHARGING
DESCRIPTION.........................19
OPERATION...........................19
DIAGNOSIS AND TESTING - CHARGING
SYSTEM............................19
SPECIFICATIONS
GENERATOR RATINGS.................20
SPECIFICATIONS - TORQUE - GENERATOR
/ CHARGING SYSTEM..................20
BATTERY TEMPERATURE SENSOR
DESCRIPTION.........................21OPERATION...........................21
REMOVAL.............................21
INSTALLATION.........................21
GENERATOR
DESCRIPTION.........................21
OPERATION...........................21
REMOVAL.............................22
INSTALLATION.........................24
VOLTAGE REGULATOR
DESCRIPTION.........................25
OPERATION...........................25
CHARGING
DESCRIPTION
The charging system consists of:
²Generator
²Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM). Elec-
tronic Control Module (ECM) for diesel engines.
²Ignition switch
²Battery (refer to 8, Battery for information)
²Battery temperature sensor
²Check Gauges Lamp (if equipped)
²Voltmeter (refer to 8, Instrument Panel and
Gauges for information)
²Wiring harness and connections (refer to 8, Wir-
ing Diagrams for information)
OPERATION
The charging system is turned on and off with the
ignition switch. The system is on when the engine is
running and the ASD relay is energized. When the
ASD relay is on, voltage is supplied to the ASD relay
sense circuit at the PCM (ECM Diesel). This voltage
is connected through the PCM (ECM Diesel) and sup-
plied to one of the generator field terminals (Gen.
Source +) at the back of the generator.
The amount of direct current produced by the gen-
erator is controlled by the EVR (field control) cir-
cuitry contained within the PCM (ECM Diesel). This
circuitry is connected in series with the second rotor
field terminal and ground.
A battery temperature sensor, located in the bat-
tery tray housing, is used to sense battery tempera-
ture. This temperature data, along with data from
monitored line voltage, is used by the PCM (ECM
Diesel) to vary the battery charging rate. This isdone by cycling the ground path to control the
strength of the rotor magnetic field. The PCM then
compensates and regulates generator current output
accordingly.
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD-sensed systems, including EVR
(field control) circuitry, are monitored by the PCM
(ECM Diesel). Each monitored circuit is assigned a
Diagnostic Trouble Code (DTC). The PCM will store a
DTC in electronic memory for certain failures it
detects.
The Check Gauges Lamp (if equipped) monitors:
charging system voltage,engine coolant tempera-
ture and engine oil pressure. If an extreme condition
is indicated, the lamp will be illuminated. This is
done as reminder to check the three gauges. The sig-
nal to activate the lamp is sent via the CCD bus cir-
cuits. The lamp is located on the instrument panel.
Refer to 8, Instrument Panel and Gauges for addi-
tional information.
DIAGNOSIS AND TESTING - CHARGING
SYSTEM
The following procedures may be used to diagnose
the charging system if:
²the check gauges lamp (if equipped) is illumi-
nated with the engine running
²the voltmeter (if equipped) does not register
properly
²an undercharged or overcharged battery condi-
tion occurs.
Remember that an undercharged battery is often
caused by:
²accessories being left on with the engine not
running
DRCHARGING 8F - 19

SKIM cannot be repaired and, if faulty or damaged,
the unit must be replaced.
DIAGNOSIS AND TESTING
VEHICLE THEFT SECURITY SYSTEM
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO RESTRAINT SYSTEMS BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
NOTE: The most reliable, efficient, and accurate
means to diagnose the Vehicle Theft Security Sys-
tem (VTSS) and Sentry Key Immobilizer System
(SKIS) involves the use of a DRBlllTscan tool and
the proper Powertrain Diagnostic Procedures man-
ual.
The Vehicle Theft Security System (VTSS), Sentry
Key Immobilizer System (SKIS) and the Programma-
ble Communication Interface (PCI) bus network
should be diagnosed using a DRBIIItscan tool. The
DRBIIItwill allow confirmation that the PCI bus is
functional, that the Sentry Key Immobilizer Module
(SKIM) is placing the proper messages on the PCI
bus, and that the Powertrain Control Module (PCM)
and the Instrument Cluster are receiving the PCI
bus messages. Refer to the proper Powertrain or
Body Diagnostic Procedures manual.
Visually inspect the related wiring harness connec-
tors. Look for broken, bent, pushed out or corroded
terminals. If any of the conditions are present, repair
as necessary. Refer to Wiring Diagrams for complete
circuit descriptions and diagrams. Refer to 8 - ELEC-
TRICAL/ELECTRONIC CONTROL MODULES/SEN-
TRY KEY IMMOBILIZER MODULE - REMOVAL for
SKIM replacement.
STANDARD PROCEDURE
CONFIGURING A NEW MODULE / SWITCH
OPERATING MODES
To configure a new module or to switch operating
modes, a DRBIIItscan tool must be used.
(1) Hook up the DRBIIItscan tool to the Data
Link Connector (DLC).
(2) With the key in the ignition, turn the key to
the RUN position.(3) After the DRBIIItscan tool initialization, per-
form the following:
(a) Select ªTheft Alarm.º
(b) Select ªVTSS.º
(c) Select ªMiscellaneous.º
(4) Once in the ªMiscellaneousº screen:
(a) If you wish to configure a new module, select
ªConfigure Module.º
(b) If you wish to put the module into customer
usage mode, select ªEnable VTSS.º
(c) If you wish to put the module into dealer lot
mode, select ªDealer Lot.º
SENTRY KEY IMMOBILIZER SYSTEM
INITIALIZATION
The Sentry Key Immobilizer System (SKIS) initial-
ization should be performed following a Sentry Key
Immobilizer Module (SKIM) replacement.
It can be summarized by the following:
(1) Obtain the vehicles unique PIN number
assigned to it's original SKIM from the vehicle
owner, the vehicle's invoice or from Chrysler's Cus-
tomer Center.
(2) With the DRBIIItscan tool, select ªTheft
Alarm,º ªSKIM,º Miscellaneous.º Select ªSKIM Mod-
ule Replacedº function and the DRBIIItwill prompt
you through the following steps.
(3) Enter secured access mode using the unique
four digit PIN number.
(4) Program the vehicle's VIN number into the
SKIM's memory.
(5) Program the country code into the SKIM's
memory (U.S.).
(6) Transfer the vehicle's unique Secret Key data
from the PCM. This process will require the SKIM to
be insecured access mode. The PIN number must
be entered into the DRBIIItbefore the SKIM will
entersecured access mode. Oncesecured access
modeis active, the SKIM will remain in that mode
for 60 seconds.
(7) Program all customer keys into the SKIM's
memory. This required that the SKIM be insecured
access modeThe SKIM will immediately exit
secured access modeafter each key is pro-
grammed.
NOTE: If a PCM is replaced, the unique ªSecret
Keyº data must be transferred from the SKIM to the
PCM. This procedure requires the SKIM to be
placed in SECURED ACCESS MODE using the four
digit PIN code.
DRVEHICLE THEFT SECURITY 8Q - 3
VEHICLE THEFT SECURITY (Continued)

and coil are the only serviced parts on the compres-
sor.
A/C compressor clutch engagement is controlled by
several components: the A/C-heater control, A/C pres-
sure transducer, A/C compressor clutch relay, evapo-
rator temperature sensor and the powertrain control
module (PCM). The PCM may delay compressor
clutch engagement for up to thirty seconds (Refer to
8 - ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/POWERTRAIN CONTROL MODULE -
DESCRIPTION).
DIAGNOSIS AND TESTING - A/C COMPRESSOR
CLUTCH COIL
For circuit descriptions and diagrams, (Refer to
Appropriate Wiring Information). The battery must
be fully-charged before performing the following
tests. Refer to Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the A/C-heater controls in any A/C mode,
and the blower motor switch in the lowest speed
position, start the engine and run it at normal idle.
(3) The compressor clutch coil voltage should read
within 0.2 volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within 0.2 volts of the battery voltage, test the clutch
coil feed circuit for excessive voltage drop and repair
as required. If there is no voltage reading at the
clutch coil, use a DRB IIItscan tool and (Refer to
Appropriate Diagnostic Information) for testing of thecompressor clutch circuit and PCM control. The fol-
lowing components must be checked and repaired as
required before you can complete testing of the clutch
coil:
²Fuses in the junction block and the power distri-
bution center (PDC)
²A/C-heater control
²A/C compressor clutch relay
²A/C pressure transducer
²Evaporator temperature sensor
²Powertrain control module (PCM)
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is within
specifications with the electrical system voltage at
11.5 to 12.5 volts (Refer to 24 - HEATING & AIR
CONDITIONING - SPECIFICATIONS). This should
only be checked with the work area temperature at
21É C (70É F). If system voltage is more than 12.5
volts, add electrical loads by turning on electrical
accessories until the system voltage drops below 12.5
volts.
(a) If the clutch coil current reading is above
specifications, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
STANDARD PROCEDURE - A/C COMPRESSOR
CLUTCH BREAK-IN
After a new compressor clutch has been installed,
cycle the compressor clutch approximately twenty
times (five seconds on, then five seconds off). During
this procedure, set the A/C-heater control to the
Recirculation Mode, the blower motor switch in the
highest speed position, and the engine speed at 1500
to 2000 rpm. This procedure (burnishing) will seat
the opposing friction surfaces and provide a higher
compressor clutch torque capability.
REMOVAL
The refrigerant system can remain fully-charged
during compressor clutch, rotor, or coil replacement.
The compressor clutch can be serviced in the vehicle.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the serpentine drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(3) Disconnect the compressor clutch coil wire har-
ness connector.
(4) Remove the bolts that secure the compressor to
the mounting bracket.
(5) Remove the compressor from the mounting
bracket. Support the compressor in the engine com-
partment while servicing the clutch.
Fig. 1 Compressor Clutch - Typical
1 - CLUTCH PLATE
2 - SHAFT KEY (not used on KJ)
3 - ROTOR
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
24 - 10 CONTROLSDR
A/C COMPRESSOR CLUTCH/COIL (Continued)

spikes and electromagnetic interference that can be
generated as the electromagnetic field of the relay
coil collapses.
The A/C compressor clutch relay terminals are con-
nected to the vehicle electrical system through a
receptacle in the integrated power module (IPM). The
inputs and outputs of the A/C compressor clutch
relay include:
²The common feed terminal (30) receives a bat-
tery current input from a fuse in the IPM through a
fused B(+) circuit at all times.
²The coil ground terminal (86) receives a ground
input from the PCM/ECM through the A/C compres-
sor clutch relay control circuit only when the PCM/
ECM electronically pulls the control circuit to
ground.
²The coil battery terminal (85) receives a battery
current input from PTC 1 in the IPM through a
fused ignition switch output (run) circuit only when
the ignition switch is in the On position.
²The normally open terminal (87) provides a bat-
tery current output to the compressor clutch coil
through the A/C compressor clutch relay output cir-
cuit only when the A/C compressor clutch relay coil is
energized.
²The normally closed terminal (87A) is not con-
nected to any circuit in this application, but provides
a battery current output only when the A/C compres-
sor clutch relay coil is de-energized.
Refer to the appropriate wiring information for
diagnosis and testing of the micro-relay and for com-
plete HVAC wiring diagrams.
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the cover from the integrated power
module (IPM) (Fig. 11).
(3) Refer to the fuse and relay layout label on the
IPM cover for compressor clutch relay identification
and location.
(4) Remove the A/C compressor clutch relay from
the IPM.
INSTALLATION
(1) See the fuse and relay layout label affixed to
the underside of the IPM cover for A/C compressor
clutch relay location.
(2) Position the A/C compressor clutch relay in the
proper receptacle in the IPM.
(3) Align the A/C compressor clutch relay termi-
nals with the terminal cavities in the IPM receptacle.
(4) Push down firmly on the A/C compressor clutch
relay until the terminals are fully seated in the ter-
minal cavities in the IPM receptacle.
(5) Install the cover onto the IPM.(6) Reconnect the negative battery cable.
A/C HEATER CONTROL
DESCRIPTION
The heater and air conditioning systems use elec-
trical controls. These controls provide the vehicle
operator with a number of setting options to help
control the climate and comfort within the vehicle.
The A/C-heater control for the Single Zone system
(Fig. 12) or Dual Zone system (Fig. 13) is located to
the right of the instrument cluster on the instrument
panel.
The Single Zone control panel contains a rotary-
type temperature control switch, a rotary-type mode
control switch and a rotary-type blower motor speed
switch. The A/C-heater control also has a push but-
ton to activate the optional heated side view mirror
defroster elements and to turn the A/C on.
The Dual Zone control panel contains a pair of slid-
er-type temperature control switches, a rotary-type
mode control switch and a rotary-type blower motor
speed switch. The control also has buttons to activate
the optional heated sideview mirror defroster ele-
ments, turn the A/C on and set the system to Max
A/C.
The A/C-heater control panel cannot be repaired. If
faulty or damaged, the entire unit must be replaced.
Fig. 11 Integrated Power Module (IPM)
1 - BATTERY
2 - INTEGRATED POWER MODULE (IPM)
24 - 14 CONTROLSDR
A/C COMPRESSOR CLUTCH RELAY (Continued)