Content .. 132 133 134 135 ..

Jeep XJ. Manual - part 134

SEAT HEAT INTERFACE MODULE DIAGNOSTIC ROUTINES

FAILURE MODE

SWITCH “HI” TELLTALE

SWITCH “LO” TELLTALE

Shorted Heating Element

Flashing

Open Heating Element

Flashing

Off

NTC Value Out of Range

Off

Flashing

Before testing the individual components in the

heated seat system, check the following:

• If the heated seat switch backlighting does not

illuminate with the ignition switch in the ON posi-
tion, check the fuse in the junction block. If the fuse
is OK, see Heated Seat Switch Backlighting in the
Diagnosis and Testing section of this group. If not
OK, repair the shorted circuit or component as
required and replace the faulty fuse.

• If the heated seat switch telltales do not illumi-

nate with the ignition switch in the ON position, but
the heating elements do heat, see Heated Seat
Switch Telltales in the Diagnosis and Testing section
of this group.

• If the heated seat switch backlighting illumi-

nates with the ignition switch in the ON position,
but the heating elements do not heat and the tell-
tales do not illuminate, check the circuit breaker in
the junction block. If the circuit breaker is OK, see
Heated Seat Switch Multiplexed Resistances in the
Diagnosis and Testing section of this group. If not
OK, replace the faulty circuit breaker.

• If the heated seat switch backlighting illumi-

nates and the telltales illuminate, but the heating
elements do not heat; see Heated Seat Element in
the Diagnosis and Testing section of this group.

HEATED SEAT SWITCH

For circuit descriptions and diagrams, refer to 8W -

63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.

WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,

REFER

GROUP

PASSIVE

RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING

WHEEL,

STEERING

COLUMN,

INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.

BACKLIGHTING

(1) Disconnect and isolate the battery negative

cable

(2) Remove the heated seat switch assembly from

the center console. Remove the connector from the

suspect switch. Check for continuity between the
ground circuit cavity of the 6-way heated seat switch
wire harness connector and a good ground. There
should be continuity. If OK, go to Step 3. If not OK,
repair the open circuit as required.

(3) Connect the battery negative cable. Turn the

ignition switch to the ON position. Check for battery
voltage at the fused ignition switch output circuit
cavity of the 6-way heated seat switch wire harness
connector. If OK, turn the ignition switch to the OFF
position, disconnect and isolate the battery negative
cable, and replace the heated seat switch. If not OK,
repair the open circuit as required.

TELLTALES

(1) Replace the heated seat switch with a known

good unit and test the operation of the switch tell-
tales. If OK, discard the faulty heated seat switch. If
not OK, see Seat Heat Interface Module in the Diag-
nosis and Testing section of this group.

MULTIPLEXED RESISTANCES

(1) Disconnect and isolate the battery negative

cable.

(2) Remove the heated seat switch assembly from

the center console. Remove the connector from the
suspect switch.

(3) With the suspect heated seat switch in the

NEUTRAL position, using an ohmmeter, measure the
resistance between the fused ignition switch output
circuit terminal and the heated seat switch output
circuit terminal in the 6-way connector receptacle on
the back of the switch. The resistance reading should
be about 2.2. Kohms. If OK, go to Step 4. If not OK,
replace the faulty switch.

(4) Hold the suspect heated seat switch in the LO

position. Using an ohmmeter, check the resistance
between the fused ignition switch output circuit ter-
minal and the heated seat switch output circuit ter-
minal in the 6-way connector receptacle on the back
of the switch. The resistance reading should be about
414 Ohms. If OK, go to Step 5. If not OK, replace the
faulty switch.

(5) Hold the suspect heated seat switch in the HI

8N - 10

ELECTRICALLY HEATED SYSTEMS

DIAGNOSIS AND TESTING (Continued)

of the switch. The resistance reading should be about
32.5 Ohms. If OK, see Heated Seat Relay in the
Diagnosis and Testing section of this group. If not
OK, replace the faulty switch.

HEATED SEAT ELEMENT and SENSOR

The wire harness connectors for the seat cushion

and seat back heating elements are located under the
seat, near the rear edge of the seat cushion frame.
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.

SEAT CUSHION

(1) Disconnect and isolate the battery negative

cable. Unplug the 4-way heated seat cushion wire
harness connector.

(2) Check for continuity between the two heated

seat element circuit cavities of the seat cushion cover
half of the heated seat cushion wire harness connec-
tor. There should be continuity. If OK, go to Step 3. If
not OK, replace the faulty seat cushion cover.

(3) Check for continuity between one of the heated

seat element circuit cavities of the seat cushion cover
half of the heated seat cushion wire harness connec-
tor and the seat cushion frame. There should be no
continuity. If OK, see Seat Back in the Diagnosis and
Testing section of this group. If not OK, replace the
faulty seat cushion cover.

SEAT BACK

(1) Disconnect and isolate the battery negative

cable. Unplug the 2-way heated seat back wire har-
ness connector.

(2) Check for continuity between the heated seat

element circuit cavity and the ground circuit cavity of
the seat back cover half of the heated seat back wire
harness connector. There should be continuity. If OK,
go to Step 3. If not OK, replace the faulty seat back
cover.

(3) Check for continuity between the heated seat

element circuit cavity of the seat back cover half of
the heated seat back wire harness connector and the
seat back frame. There should be no continuity. If
OK, see Heated Seat Sensor in the Diagnosis and
Testing section of this group. If not OK, replace the
faulty seat back cover.

HEATED SEAT SENSOR

The wire harness connector for the seat cushion

heating element and sensor are located under the
seat, near the rear edge of the seat cushion frame.
For circuit descriptions and diagrams, refer to 8W -
63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.

(1) Disconnect and isolate the battery negative

cable. Unplug the 4-way heated seat cushion wire
harness connector.

(2) Using

ohmmeter,

check

the

resistance

between the heated seat sensor input circuit cavity
and the heated seat sensor feed circuit cavity of the
seat cushion cover half of the heated seat cushion
wire harness connector. The sensor resistance should
be between 1 Kohm and 200 Kohms. If OK, see
Heated Seat Relay in the Diagnosis and Testing sec-
tion of this group. If not OK, replace the faulty seat
cushion cover.

HEATED SEAT RELAY

For circuit descriptions and diagrams, refer to 8W -

63 - Power Seat With Heated Seats in Group 8W -
Wiring Diagrams.

(1) Disconnect and isolate the battery negative

cable. Unplug the 8-way heated seat relay connector.

(2) Check for continuity between the ground cir-

cuit cavity of the 8-way heated seat relay wire har-
ness connector and a good ground. There should be
continuity. If OK, go to Step 3. If not OK, repair the
open circuit as required.

(3) Connect the battery negative cable. Check for

battery voltage at the battery feed circuit cavity (pin
8) of the 8-way heated seat relay wire harness con-
nector. If OK, go to Step 4. If not OK, repair the open
circuit as required.

(4) Turn the ignition switch to the ON position.

Check for battery voltage at the fused ignition switch
output circuit cavity of the 8-way heated seat relay
wire harness connector. If OK, turn the ignition
switch to the OFF position, disconnect and isolate
the battery negative cable, and go to Step 5. If not
OK, repair the open circuit as required.

(5) Unplug the 14-way seat heat interface module

(SHIM) connector. Check for continuity between the
two switched battery feed cavities of the 14-way
SHIM wire harness connector and the switched bat-
tery feed cavity of the 8-way heated seat relay wire
harness connector. If OK, reconnect the heated seat
relay wire harness connector, and go to Step 6. If not
OK, repair the open circuit as required.

(6) Connect the battery negative cable. Turn the

ignition switch to the ON position. Check for battery
voltage at the switched battery feed cavities of the
14-way SHIM wire harness connector. If OK, turn
the ignition switch to the OFF position, disconnect
and isolate the battery negative cable, and see Seat
Heat Interface Module in the diagnosis and testing
section of this group. If not OK, replace the heated
seat relay.

ELECTRICALLY HEATED SYSTEMS

8N - 11

DIAGNOSIS AND TESTING (Continued)

SEAT HEAT INTERFACE MODULE

Before testing the seat heat interface module, test

the heated seat switch, the heated seat elements, and
the heated seat sensor as described in the Diagnosis
and Testing section of this group. If testing of the
heated seat switch, elements, and sensor reveals no
problems, proceed as follows. For circuit descriptions
and diagrams, refer to 8W - 63 - Power Seat With
Heated Seats in Group 8W - Wiring Diagrams.

(1) Replace the seat heat interface module with a

known good unit and test the operation of the heated
seats. If OK, discard the faulty seat heat interface
module. If not OK, go to Step 2.

(2) Test each of the circuits from the heated seat

switch, heated seat relay, heated seat elements, and
heated seat sensor to the seat heat interface module.
Repair any short or open circuits as required.

REMOVAL AND INSTALLATION

HEATED SEAT SWITCH

WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,

REFER

GROUP

PASSIVE

RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING

WHEEL,

STEERING

COLUMN,

INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.

(1) Disconnect and isolate the battery negative

cable.

(2) Using a trim stick or another suitable wide

flat-bladed tool, gently pry around the perimeter
edges of the heated switch assembly bezel to release
the assembly from the console. Remove the assembly
from the console.

(3) Pull the switch assembly out from the console

far enough to access and unplug the wire harness
connectors.

(4) Remove the heated seat switch assembly from

the console.

(5) Remove the heated seat switch(es) from the

heated seat switch assembly.

(6) Reverse the removal procedures to install.

SEAT HEAT INTERFACE MODULE

(1) Move the right power seat adjuster to its full

up and full rear stop positions.

(2) Disconnect and isolate the battery negative

cable.

(3) Unhook the seat cushion cover retainer from

the seat cushion frame and pull back the seat cush-
ion cover.

(4) Pull back the seat cushion to allow access to

the Seat Heat Interface Module (SHIM).

(5) Pull the SHIM upward to release the two

mounting fasteners from either the module or the
mounting bracket. Unplug the wire harness connec-
tor from the module (Fig. 2).

WARNING: THERE

ARE

MANY

SHARP

METAL

EDGES ON THE SEAT CUSHION FRAME AND SEAT
ADJUSTER RAILS UNDER THE SEAT. WHEN PER-
FORMING THIS SERVICE, A LONG-SLEEVED SHIRT
AND GLOVES SHOULD BE WORN IN ORDER TO
AVOID UNNECESSARY CUTS AND ABRASIONS TO
EXPOSED SKIN.

(6) Reverse the removal procedures to install. Be

certain that the SHIM terminals are aligned with the
cavities in the wire harness connector before pushing
the module firmly into place.

HEATED SEAT RELAY

(1) Move the right power seat adjuster to its full

up and full rear stop positions.

(2) Disconnect and isolate the battery negative

cable.

(3) Unhook the seat cushion cover retainer from

the seat cushion frame and pull back the seat cush-
ion cover.

(4) Pull back the seat cushion to allow access to

the Heated Seat Relay.

Fig. 2 Seat Heat Interface Module Remove/Install

1 – SEAT CUSHION FRAME
2 – SEAT HEAT INTERFACE MODULE
3 – WIRE HARNESS CONNECTOR
4 – POWER SEAT TRACK FRONT BRACKET

8N - 12

ELECTRICALLY HEATED SYSTEMS

DIAGNOSIS AND TESTING (Continued)

(5) Cut the Christmas tree fastener to remove the

Heated Seat Relay fastener from the mounting
bracket. Unplug the wire harness connector from the
relay (Fig. 3).

(6) Reverse the removal procedures to install. A

new Christmas tree fastener must be used to mount
the relay. Be certain that the relay terminals are
aligned with the cavities in the wire harness connec-
tor before pushing the relay firmly into place.

Fig. 3 Heated Seat Relay Remove/Install

1 – HEATED SEAT RELAY
2 – SEAT CUSHION FRAME
3 – WIRE HARNESS CONNECTOR
4 – POWER SEAT TRACK FRONT BRACKET

ELECTRICALLY HEATED SYSTEMS

8N - 13

REMOVAL AND INSTALLATION (Continued)

Content .. 132 133 134 135 ..