1998 DODGE RAM 1500 Control module

(2) Install the screws holding the EVIC module in
the overhead console.
(3) Connect the EVIC module electrical connector.
(4) Install the overhead console on the headlin-
er(Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE - INSTALLATION).
(5) Connect the battery negative cable.
(6) Check EVIC module function.
NOTE: If a new EVIC module has been installed, the
compass will have to be calibrated and the variance
set. Refer to Compass Variation Adjustment and
Compass Calibration in the Standard Procedures
section of this group for the procedures.
AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the over-
head console. The ambient temperature messages are
received from the Front Control Module (FCM) over
the Programmable Communications Interface (PCI)
J1850 data bus circuit. The FCM receives a hard
wired input from the ambient temperature sensor
(Fig. 7). The ambient temperature sensor is a vari-
able resistor mounted to the underside of the hood,
in the engine compartment.
For more information on the front control module,
refer toFront Control Modulein the Electronic
Control Modules section of this manual. For complete
circuit diagrams, refer toWiring. The ambient tem-
perature sensor cannot be adjusted or repaired and,
if faulty or damaged, it must be replaced.
OPERATION
The ambient temperature sensor is a variable
resistor that operates on a five-volt reference signal
sent to it by the Front Control Module. The resis-
tance in the sensor changes as temperature changes,
changing the temperature sensor signal circuit volt-
age to the Front Control Module. Based upon the
resistance in the sensor, the Front Control Modulesenses a specific voltage on the temperature sensor
signal circuit, which it is programmed to correspond
to a specific temperature. The Front Control Module
then sends the proper ambient temperature mes-
sages to the EVIC, CMTC over the PCI J1850 data
bus.
The temperature function is supported by the
ambient temperature sensor, a wiring circuit, the
Front Control Module, the Programmable Communi-
cations Interface (PCI) data bus, and a portion of the
Electronics module. If any portion of the ambient
temperature sensor circuit fails, the Front Control
Module will self-diagnose the circuit.
For complete circuit diagrams, refer toWiring.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector.
(2) Measure the resistance of the ambient temper-
ature sensor. At 24É C (75É F), the sensor resistance
should be approximately 10.3 kilohms. At 30É C (86É
F), the sensor resistance should be approximately
7.57 kilohms. The sensor resistance should decrease
as the temperature rises. If OK, refer toDiagnosis
and Testing - Ambient Temperature Sensor Cir-
cuitin this group. If not OK, replace the faulty
ambient temperature sensor.
NOTE: The ambient temperature sensor is a very
sensitive device. When testing, be certain the tem-
perature sensor has had time to stabilize (room
temperature) before attempting to read the sensor
resistance. Failure to let the ambient temperature
sensor temperature stabilize could result in a mis-
leading test.
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR CIRCUIT
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector and the Front Control Module wire
harness connector.
(2) Connect a jumper wire between the two termi-
nals of the ambient temperature sensor wire harness
connector.
(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the Front Control Module wire har-
Fig. 7 Ambient Temperature Sensor - Typical
8M - 10 MESSAGE SYSTEMSDR
ELECTRONIC VEHICLE INFO CENTER (Continued)

ness connector. There should be continuity. If OK, go
to Step 4. If not OK, repair the open sensor return or
signal circuit as required.
(4) Remove the jumper wire from the ambient tem-
perature sensor wire harness connector. Check for
continuity between the sensor return circuit cavity of
the Front Control Module wire harness connector
and a good ground. There should be no continuity. If
OK, go to Step 5. If not OK, repair the shorted sen-
sor return circuit as required.
(5) Check for continuity between the ambient tem-
perature sensor signal circuit cavity of the Front
Control Module wire harness connector and a good
ground. There should be no continuity. If OK, refer to
Diagnosis and Testing - Overhead Consolein
this group. If not OK, repair the shorted ambient
temperature sensor signal circuit as required.
REMOVAL
(1) Open the hood.
(2) Disconnect and isolate the battery negative
cable.
(3) Working on the underside of the hood, remove
screw holding sensor to hood panel.
(4) Disconnect the sensor electrical connector and
remove sensor from vehicle.
INSTALLATION
(1) Connect the sensor electrical connector.
(2) Working on the underside of the hood, install
screw holding sensor to hood panel.
(3) Connect the battery negative cable.
(4) Close the hood.
UNIVERSAL TRANSMITTER
DESCRIPTION
Some DR models are equipped with a universal
transmitter transceiver. The universal transmitter is
integral to the Electronic Vehicle Information Center
(EVIC) and the Compass Mini-Trip Computer
(CMTC), which is located in the overhead console.
The only visible component of the universal transmit-
ter are the three transmitter push buttons centered
between the modules push buttons located just rear-
ward of the display screen in the overhead console.
The three universal transmitter push buttons are
identified with one, two or three light indicators so
that they be easily identified.
Each of the three universal transmitter push but-
tons control an independent radio transmitter chan-
nel. Each of these three channels can be trained to
transmit a different radio frequency signal for the
remote operation of garage door openers, motorized
gate openers, home or office lighting, security sys-tems or just about any other device that can be
equipped with a radio receiver in the 286 to 399
MegaHertz (MHz) frequency range for remote opera-
tion. The universal transmitter is capable of operat-
ing systems using either rolling code or non-rolling
code technology.
The electronics module displays messages and a
small house-shaped icon with one, two or three dots
corresponding to the three transmitter buttons to
indicate the status of the universal transmitter. The
EVIC messages are:
²Clearing Channels- Indicates that all of the
transmitter codes stored in the universal transmitter
have been successfully cleared.
²Channel ªXº Training- Indicates that the uni-
versal transmitter is in its transmitter learning
mode.
²Channel ªXº Trained- Indicates that the uni-
versal transmitter has successfully acquired a new
transmitter code.
²Channel ªXº Transmitting- Indicates that a
trained universal transmitter button has been
depressed and that the universal transmitter is
transmitting.
The universal transmitter cannot be repaired, and
is available for service only as a unit with the EVIC
or CMTC modules. If any part of the universal trans-
mitter is faulty or damaged, the complete EVIC or
CMTC module must be replaced.
OPERATION
The universal transmitter operates on a non-
switched source of battery current so the unit will
remain functional, regardless of the ignition switch
position. For more information on the features, pro-
gramming procedures and operation of the universal
transmitter, see the owner's manual in the vehicle
glove box.
DIAGNOSIS AND TESTING - UNIVERSAL
TRANSMITTER
If the Universal Transmitter is inoperative, but the
Electronic Vehicle Information Center (EVIC) is oper-
ating normally, see the owner's manual in the vehicle
glove box for instructions on training the Transmit-
ter. Retrain the Transmitter with a known good
transmitter as instructed in the owner's manual and
test the Transmitter operation again. If the unit is
still inoperative, test the universal transmitter with
Radio Frequency Detector special tool. If both the
Transmitter and the EVIC module are inoperative,
refer toElectronic Vehicle Information Center
Diagnosis and Testingin this group for further
diagnosis. For complete circuit diagrams, refer to
Wiring Diagrams. (Fig. 8) as described below:
DRMESSAGE SYSTEMS 8M - 11
AMBIENT TEMP SENSOR (Continued)

POWER LOCK SWITCH
DIAGNOSIS AND TESTING - POWER LOCK
SWITCH
The Light-Emitting Diode (LED) illumination lamp
of the power lock switch receives battery current
through a fuse in the Integrated Power Module (IPM)
on a fused ignition switch output (run) circuit. The
power lock switch on the driver side front door trim
panel is integral to the driver door module. (Refer to
8 - ELECTRICAL/POWER LOCKS/DOOR MODULE
- DIAGNOSIS AND TESTING). If the power lock
switch operates, but the LED is inoperative, check
for battery current at the switch with the ignition
switch in the On position. If OK, replace the faulty
switch. Refer to the appropriate wiring information.
(1) Disconnect and isolate the battery negative
cable. Remove the power lock switch from the door
trim panel. Disconnect the door wire harness connec-
tor for the power lock switch from the switch connec-
tor receptacle.
(2) Test the power lock switch resistance. See the
Power Lock Switch Test chart to determine if the
resistance is correct for the switch in each switch
position (Fig. 1). If not OK, replace the faulty power
lock switch as required.
POWER LOCK SWITCH TEST TABLE
SWITCH POSITION RESISTANCE BETWEEN
PINS1&5
NEUTRAL 10 KILOHMS  1%
LOCK 820 OHMS  5%
UNLOCK 330 OHMS  5%
REMOVAL
The power lock switch on the driver side front door
trim panel is integral to the driver door module.
(Refer to 8 - ELECTRICAL/POWER LOCKS/DOOR
MODULE - REMOVAL).
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the door trim panel (Refer to 23 -
BODY/DOOR - FRONT/TRIM PANEL - REMOVAL).
(3) Remove the switch from the trim panel bezel.
INSTALLATION
(1) Insert switch to trim panel bezel.
(2) Install door trim panel (Refer to 23 - BODY/
DOOR - FRONT/TRIM PANEL - INSTALLATION).
(3) Connect battery negative cable.
DOOR LOCK MOTOR
DESCRIPTION
The lock mechanisms are actuated by a reversible
electric motor mounted within each door. The power
lock motors are integral to the door latch units.
The power lock motors cannot be adjusted or
repaired and, if faulty or damaged, the door latch
unit must be replaced.
OPERATION
The door lock motors are controlled by the instru-
ment cluster. A positive and negative battery connec-
tion to the two motor terminals will cause the motor
to move in one direction. Reversing the current will
cause the motor to move in the opposite direction.
DIAGNOSIS AND TESTING - DOOR LOCK
MOTOR
The most reliable, efficient, and accurate means to
diagnose the power lock system requires the use of a
DRBIIItscan tool and the proper Diagnostic Proce-
dures manual.
Refer to the appropriate wiring information.
Fig. 1 Power Lock Switch Connector Receptacle
8N - 4 POWER LOCKSDR

DRIVER DOOR MODULE
DESCRIPTION
A Driver Door Module (DDM) is used on all models
equipped with power locks, power windows, and
power mirrors. The DDM houses the following
switches:
²Power Lock Switch- The DDM includes a
two-way, momentary, resistor multiplexed switch to
control the power lock system.
²Power Mirror Selector Switch- A three-posi-
tion rocker switch in the DDM selects the right or
left power mirror for adjustment, or turns the power
mirror system Off.
²Power Mirror Adjustment Switches- Four
momentary, arrowhead shaped, directional switches
allow the driver to adjust the selected power mirror
in the Up, Down, Right, or Left directions.
²Power Window Lockout Switch- A two-way,
latching, push-button switch in the DDM allows the
vehicle operator to lock out the power window
switches on each passenger door so that the passen-
ger door power windows may be operated only from
the master switches in the DDM.
²Power Window Switches- The DDM houses a
two-way, momentary power window switch for the
driver side front door. This switch also has a second
detent in the Down direction and internal circuitry to
provide an Auto-Down feature for the driver side
front door power window. In addition to the power
window switch for its own door, the DDM houses
individual master switches for each passenger door
power window.
The DDM also incorporates several green Light-
Emitting Diodes (LEDs) that illuminate the power
lock and power window switch paddles, and the
power mirror switch directional buttons to improve
switch visibility in dark ambient lighting conditions.
The DDM cannot be adjusted or repaired and, if
faulty or damaged, the entire DDM unit must be
replaced.
OPERATION
The Driver Door Module (DDM) combines a power
lock switch, a driver power window switch with an
Auto-down feature, master switches for each passen-
ger door power window, a power window lockout
switch, a power mirror selector switch, and four
power mirror adjustment switches in a single unit.
The switches in the DDM can be diagnosed using
conventional diagnostic tools and methods.
Power Lock Switch
The DDM power lock switch circuitry is connected
in series between ground and the driver door switch
mux input of the instrument cluster. Each power lockswitch position (Lock, Unlock, and Neutral) provides
a different resistance value to the instrument cluster
input, which allows the instrument cluster to sense
the switch position. Based upon the power lock
switch input, the instrument cluster controls the bat-
tery and ground feed outputs to the individual power
lock motors to lock or unlock the door latches. The
Light-Emitting Diode (LED) in the DDM power lock
switch is connected to battery current through the
power window circuit breaker in the Integrated
Power Module (IPM) on a fused ignition switch out-
put (run-acc) circuit so that the switch will be illumi-
nated whenever the ignition switch is in the On or
Accessory positions.
Power Window Switches
The DDM power window switch circuitry is con-
nected to battery current through a circuit breaker in
the Integrated Power Module (IPM) on a fused igni-
tion switch output (run-acc) circuit so that the power
windows will operate whenever the ignition switch is
in the On or Accessory positions. Each two-way,
momentary master passenger power window switch
in the DDM provides battery current and ground to
the individual power window switches on each pas-
senger door so that the power window switch controls
the battery current and ground feeds to its respective
power window motor. The DDM switch for the driver
side front door power window is labeled ªAutoº and
includes an auto-down feature. When this switch is
depressed to a second momentary detent position and
released, the driver door power window is automati-
cally operated through an internal circuit and relay
to its fully lowered position. The Auto-down event is
cancelled if the switch paddle is depressed a second
time in either the Up or Down direction. When the
two position window lockout switch in the DDM is
depressed and latched in the lockout position, the
battery current feed to each of the individual passen-
ger power window switches is interrupted so that the
passenger door power windows can only be operated
from the master switches in the DDM. The window
lockout switch also controls the battery current feed
for the LED in each passenger power window switch
so that the switch will not be illuminated when it is
locked out.
Power Mirror Switches
The DDM power mirror switch circuitry is con-
nected to battery current through a fuse in the IPM
on a fused B(+) circuit so that the power mirrors
remain operational regardless of the ignition switch
position. A rocker type selector switch has three posi-
tions, one to select the right mirror, one to select the
left mirror, and a neutral Off position. After the right
or left mirror is selected, one of four directional but-
DRPOWER LOCKS 8N - 5

tons is depressed to move the selected mirror Up,
Down, Right or Left. The DDM power mirror switch
circuitry controls the battery current and ground
feeds to each of the four (two in each mirror head)
power mirror motors. The Light-Emitting Diode
(LED) in the DDM power mirror switch is connected
to battery current through the power window circuit
breaker in the IPM on a fused ignition switch output
(run-acc) circuit so that the switch directional but-
tons will be illuminated whenever the ignition switch
is in the On or Accessory positions.
DIAGNOSIS AND TESTING - DRIVER DOOR
MODULE
The Light-Emitting Diode (LED) illumination
lamps for all of the Driver Door Module (DDM)
power window, power lock, and power mirror
switches receive battery current through the power
window circuit breaker in the Integrated Power Mod-
ule (IPM). If all of the LEDs are inoperative in the
DDM, be certain to diagnose the power window sys-
tem before replacing the switch unit. (Refer to 8 -
ELECTRICAL/POWER WINDOWS - DIAGNOSIS
AND TESTING). If only one LED in the DDM is
inoperative, replace the faulty DDM. If the driver
side front door power window operates in a normal
manner, but the Auto-Down feature is inoperative,
replace the faulty DDM. Refer to the appropriate wir-
ing information.
(1) Disconnect and isolate the battery negative
cable. Remove the DDM from the door trim panel.
Disconnect the door wire harness connectors for the
DDM from the DDM connector receptacles.
(2) Test the DDM switch continuity. See the Driver
Door Module Switch Tests chart to determine if the
continuity is correct for the suspect switches in each
switch position (Fig. 2) and/or (Fig. 3). If not OK,
replace the faulty DDM as required.
DRIVER DOOR MODULE SWITCH TESTS
POWER LOCK SWITCH
SWITCH POSITIONRESISTANCE BETWEEN
CONNECTOR C-1 PINS
7&11
NEUTRAL 10 KILOHMS   1%
LOCK 820 OHMS   5%
UNLOCK 330 OHMS   5%
POWER MIRROR SWITCH
SWITCH POSITIONCONTINUITY BETWEEN
PINS OF CONNECTOR
C-2
LEFT MIRROR SELECTED
UP PINS1&3
DOWN PINS2&3
RIGHT PINS2&3
LEFT PINS3&6
RIGHT MIRROR SELECTED
UP PINS3&7
DOWN PINS2&3
RIGHT PINS2&3
LEFT PINS3&4
POWER WINDOW SWITCH
SWITCH POSITION CONTINUITY BETWEEN
PINS OF CONNECTOR
C-1
NEUTRAL PINS1&8,PINS2&8,
PINS3&8,PINS4&8,
PINS5&8,PINS6&8,
PINS 8 & 10, PINS 8 &
12
LEFT FRONT UP PINS5&9
Fig. 2 Driver Door Module Connector C1 Receptacle
Fig. 3 Driver Door Module Connector C2 Receptacle
8N - 6 POWER LOCKSDR
DRIVER DOOR MODULE (Continued)

POWER SEATS
TABLE OF CONTENTS
page page
POWER SEATS
DESCRIPTION.........................13
OPERATION...........................13
DIAGNOSIS AND TESTING - POWER SEAT
SYSTEM............................13
DRIVER SEAT SWITCH
DESCRIPTION.........................14
OPERATION...........................14
DIAGNOSIS AND TESTING - DRIVER SEAT
SWITCH............................14
REMOVAL.............................15
INSTALLATION.........................15
PASSENGER SEAT SWITCH
DESCRIPTION.........................15
OPERATION...........................15
DIAGNOSIS AND TESTING - PASSENGER
SEAT SWITCH........................16REMOVAL.............................16
INSTALLATION.........................16
POWER SEAT TRACK
DESCRIPTION.........................16
OPERATION...........................16
DIAGNOSIS AND TESTING - POWER SEAT
TRACK.............................17
REMOVAL.............................17
INSTALLATION.........................17
LUMBAR CONTROL SWITCH
DESCRIPTION.........................17
OPERATION...........................18
REMOVAL.............................18
LUMBAR MOTOR
DESCRIPTION.........................18
OPERATION...........................18
DIAGNOSIS AND TESTING - LUMBAR MOTOR . 18
POWER SEATS
DESCRIPTION
The power seat system option allows the driver or
passenger to electrically adjust the seat position for
optimum control and comfort using the power seat
switches located on the outboard seat cushion side
shield. The power seat system allows the seating
position to be adjusted forward, rearward, front up,
front down, rear up, or rear down. The power seat
system receives battery current through a fuse in the
Integrated Power Module, regardless of the ignition
switch position. The power seat system includes the
following components:
²Driver Power Seat Switch
²Passenger Power Seat Switch
²Driver Power Seat Track
²Passenger Power Seat Track
²Power Lumbar Adjuster(s)
Some models equipped with the power seat option
also feature a power operated lumbar support in the
seat back. The power lumbar support allows the user
to inflate or deflate a bladder located in the lower
seat back to achieve optimum comfort and support in
the lower lumbar region of the spinal column. The
power lumbar support shares the battery feed circuit
of the power seat system.
Following are general descriptions of the major
components in the power seat system. Refer to
Heated Seat Systemfor information on the individ-ually controlled heated front seats. Refer to the own-
er's manual in the vehicle glove box for more
information on the features, use and operation of the
power seat system.
OPERATION
The power seat system allows the driver and/or
front passenger seating positions to be adjusted elec-
trically and independently using the separate power
seat switches found on the outboard seat cushion
side shield of each front seat. See the owner's manual
in the vehicle glove box for more information on the
features, use and operation of the power seat system.
DIAGNOSIS AND TESTING - POWER SEAT
SYSTEM
Before any testing of the power seat system is
attempted, the battery should be fully-charged and
all wire harness connections and pins checked to
ensure proper continuity and grounds. For circuit
descriptions and diagrams, refer to Wiring Diagrams.
With the dome lamp on, apply the power seat
switch in the direction of the failure. If the dome
lamp dims, the seat may be jamming. Check under
and behind the seat for binding or obstructions. If
the dome lamp does not dim, proceed with testing of
the individual components and circuits.
DRPOWER SEATS 8N - 13

DRIVER POWER SEAT SWITCH TEST TABLE
DRIVER SWITCH
POSITIONCONTINUITY BETWEEN
HORIZONTAL
FORWARDA-L, B-K
HORIZONTAL
REARWARDA-K, B-L
FRONT TILT UP A-M, B-N
FRONT TILT DOWN A-N, B-M
REAR TILT UP A-E, B-J
REAR TILT DOWN A-J, B-E
LUMBAR OFF O-P, O-R, P-R
LUMPAR UP (INFLATE) O-P, Q-R
LUMBAR DOWN
(DEFLATE)O-R, P-Q
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the seat cushion side shield from the
seat. Refer to the Body section of the service manual
for the procedure.
(3) Pull the switch bezel or side shield unit out
from the seat far enough to access the switch wire
harness connector. Gently pry the locking tabs of the
switch away from the wire harness connector and
carefully unplug the connector from the power seat
switch module.
(4) Remove the screws that secure the power seat
switch.
INSTALLATION
(1) Position the power seat switch on the seat
cushion side shield and install the screws that secure
the power seat switch to seat cushion side shield.
(2) Connect the electrical connector.
(3) Install the seat cushion side shield on the seat.
Refer to the Body section of the service manual for
the procedure.
(4) If equipped, install the screw that secures the
recliner lever to the recliner mechanism release shaft
on the outboard side of the front seat.
(5) Connect the battery negative cable.
PASSENGER SEAT SWITCH
DESCRIPTION
The power seat on this model can be adjusted in
eight different directions, up, down, front up, front
down, rear up, rear down, rearward and forward.
The power seat switch (Fig. 3) on this model has an
additional switch knob for adjusting the power lum-bar support. The power seat switch is located on the
outboard side of the seat cushion on the seat cushion
side shield. Refer to the owner's manual in the vehi-
cle glove box for more information on the power seat
switch functions and the seat adjusting procedures.
The individual switches in the power seat switch
assembly cannot be repaired. If one switch is dam-
aged or faulty, the entire power seat switch assembly
must be replaced.
OPERATION
When a power switch control knob or knobs are
actuated, a battery feed and a ground path are
applied through the switch contacts to the power seat
track or recliner adjuster motor. The selected
adjuster motor operates to move the seat track or
recliner through its drive unit in the selected direc-
tion until the switch is released, or until the travel
limit of the adjuster is reached. When the switch is
moved in the opposite direction, the battery feed and
ground path to the motor are reversed through the
switch contacts. This causes the adjuster motor to
run in the opposite direction.
No power seat switch should be held applied in any
direction after the adjuster has reached its travel
limit. The power seat adjuster motors each contain a
self-resetting circuit breaker to protect them from
overload. However, consecutive or frequent resetting
of the circuit breaker must not be allowed to con-
tinue, or the motor may be damaged.
Fig. 3 DR Power Seat Switch
1 - POWER SEAT SWITCH ASSEMBLY
2 - FRONT SEAT CUSHION ADJUSTMENT BUTTON
3 - COMPLETE SEAT ADJUSTMENT BUTTON
4 - REAR SEAT CUSHION ADJUSTMENT BUTTON
5 - LUMBAR ADJUSTMENT BUTTON
DRPOWER SEATS 8N - 15
DRIVER SEAT SWITCH (Continued)

shield that helps to shroud it from unintentional
actuation when entering or leaving the vehicle.
The power lumbar switches cannot be adjusted or
repaired and, if faulty or damaged, the seat switch
assembly must be replaced.
OPERATION
When the power lumbar switch paddle is actuated,
a battery feed and a ground path are applied through
the switch contacts to the power lumbar adjuster
motor. The motor operates to move the lumbar
adjuster through its drive unit in the selected direc-
tion until the switch is released, or until the travel
limit of the adjuster is reached. When the switch is
moved in the opposite direction, the battery feed and
ground path to the motor are reversed through the
switch contacts. This causes the motor to run in the
opposite direction.
The power lumbar switch should not be held
applied in either direction after the adjuster has
reached its travel limit. The power lumbar adjuster
motor contains a self-resetting circuit breaker to pro-
tect it from overload. However, consecutive or fre-
quent resetting of the circuit breaker must not be
allowed to continue, or the motor may be damaged.
REMOVAL
The power lumbar switch is integral with the other
power seat switches. Refer to the appropriate driver
or passenger power front seat switch removal and/or
installation procedure.
LUMBAR MOTOR
DESCRIPTION
The power lumbar seat option includes an electri-
cally operated lumbar support mechanism. The only
visible evidence of this option is the separate power
lumbar switch control paddle that is located on the
outboard seat cushion switch bezel, next to the other
power seat switch control knobs. The power lumbar
adjuster and motor are concealed beneath the seat
back trim cover and padding, where they are secured
to a molded plastic back panel and to the seat back
frame.
The power lumbar adjuster cannot be repaired, and
is serviced only as a unit with the seat back frame. If
the power lumbar adjuster or the seat back frame
are damaged or faulty, the entire seat back frame
unit must be replaced (Refer to 23 - BODY/SEATS/
SEAT BACK - REMOVAL).
OPERATION
The power lumbar adjuster mechanism includes a
reversible electric motor that is secured to theinboard side of the seat back panel and is connected
to a worm-drive gearbox. The motor and gearbox
operate the lumbar adjuster mechanism in the center
of the seat back driving a nut up or down a fixed
drive screw. The action of this nut extends or con-
tracts the plastic lumbar support band. The more
this band is contracted, the more outward pressure is
applied against the center of the seat back padding,
providing additional lumbar support.
DIAGNOSIS AND TESTING - LUMBAR MOTOR
Actuate the power lumbar switch to move the
power lumbar adjuster in each direction. The power
lumbar adjuster should move in both directions. It
should be noted that the power lumber adjuster nor-
mally operates very quietly and exhibits little visible
movement. If the power lumbar adjuster fails to oper-
ate in only one direction, move the adjuster a short
distance in the opposite direction and test again to be
certain that the adjuster is not at its travel limit. If
the power lumbar adjuster fails to operate in only
one direction, Test the appropriate power seat switch
as described in this group. If the power lumbar
adjuster fails to operate in either direction, perform
the following tests. For complete circuit diagrams,
refer toWiring.
(1) Check the power seat circuit breaker. If OK, go
to Step 2. If not OK, replace the faulty power seat
circuit breaker.
(2) Check for battery voltage at the power seat cir-
cuit breaker. If OK, go to Step 3. If not OK, repair
the open fused B(+) circuit to the fuse in the Inte-
grated Power Module as required.
(3) Remove the outboard seat cushion side shield
from the seat. Disconnect the seat wire harness con-
nector from the power lumbar switch connector
receptacle. Check for battery voltage at the fused
B(+) circuit cavity of the power seat wire harness
connector for the power lumbar switch. If OK, go to
Step 4. If not OK, repair the open fused B(+) circuit
to the power seat as required.
(4) Check for continuity between the ground cir-
cuit cavity of the power seat wire harness connector
for the power lumbar switch and a good ground.
There should be continuity. If OK, go to Step 5. If not
OK, repair the open ground circuit to ground as
required.
(5) Test the power lumbar switch. . If the switch
tests OK, test the circuits of the power seat wire har-
ness between the power lumbar adjuster motor and
the power lumbar switch for shorts or opens. If the
circuits check OK, replace the faulty seat back frame
assembly. If the circuits are not OK, repair the power
seat wire harness as required.
8N - 18 POWER SEATSDR
LUMBAR CONTROL SWITCH (Continued)