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8G - 8
HEATED SEAT SYSTEM
HEATED SEAT SYSTEM (Continued)
2ND ROW HEATED SEAT SYSTEM OPERATION
However similar, the 2nd row heated seat system
operates independently from the front heated seat
system. The 2nd row heated seat module receives
fused battery current through the Integrated Power
Module only when the ignition switch is in the ON
position. The heated seat module shares a common
ground circuit with each of the heated seat elements.
The heated seat system will only operate when the
surface temperature of the seat cushion is below the
designed temperature set points of the system. The
Low heat position set point is 35° C (95° F), and the
High heat position set point is 40° C (104° F).
A separate heated seat module contains the control
logic for the 2nd row heated seat system. The module
responds to the heated seat switch status, ignition
switch status, and the heated seat element sensor
inputs by controlling the output to the 2nd row seat
heating elements through integral solid-state relays.
When either of the 2nd row seat heated seat
switches are depressed a resistance signal is sent to
the heated seat module, signaling the module to
energize the heating element for the selected seat.
The heated seat sensor provides the heated seat
module with a low-voltage input indicating the sur-
face temperature of the seat cushion. If the surface
temperature is below the temperature set point for
the selected Low or High heated seat switch position,
the module energizes the integral solid-state relay,
which supplies battery current to the heating ele-
ments. When the sensor input indicates the correct
temperature set point has been achieved, the module
de-energizes the solid-state relay. The module will
continue to cycle the solid-state relay as needed to
maintain the temperature set point.
The heated seat system will automatically turn off
whenever the ignition switch is turned to any posi-
tion except On. If the ignition switch is turned to the
Off position while a heated seat is ON, the heated
seat will remain Off after the engine is restarted
until a 2nd row seat heated seat switch is depressed
again. This prevents the vehicles battery from being
drained by the heated seat system.
The 2nd row heated seat module also controls the
heated seat LED indicator lamps, located in both of
the 2nd row heated seat switches. The module is pro-
grammed to provide self-diagnostics, if a problem
with the 2nd row heated seat system is detected. If
the module detects faults within the heated seat sys-
tem, it will provide a visual indication of the failure
by flashing the indicator lamps in the appropriate
heated seat switch.
The module will automatically turn off the heating
elements if it detects an OPEN or HI/LOW short in the
sensor circuit, or an OPEN or LOW short in the heating
element circuit. See the owner's manual in the vehicle
glove box for more information on the features, use and
operation of the front seat heated seat system.
DIAGNOSIS AND TESTING - HEATED SEAT
SYSTEM
FRONT SEAT HEATED SEAT SYSTEM DIAGNOSIS
In order to obtain conclusive testing of the front
seat heated seat system, the Programmable Commu-
nications Interface (PCI) data bus circuit must be
checked.
The most reliable, efficient, and accurate means to
diagnose the front seat heated seat system requires
the use of a DRB III scan tool and the Service and
Body Diagnostic Manuals. The DRB III
can provide vital information to the technician trying
to find a problem with the heated seat system. Diag-
nostic logic is built into the memory heated seat
adjustable pedal module and both door modules to
help the person trying to locate the problem by the
most efficient means possible. Anytime a problem is
suspected, a DRB III scan tool should be obtained
and used to retrieve any stored fault codes in the
memory heated seat adjustable pedal module and
door modules. If the front heated seat lights blink
the MHSAPM did not respond to the door modules
command to turn on the heated seats.
If diagnostic fault codes are present in the module,
record them on a piece of paper immediately before
proceeding any further. Then, use these fault codes to
identify the problem by verifying the fault code.
Example, If the module records "DRIVER SEAT
HEAT OUTPUT OPEN" fault code, locate the diag-
nostic procedure for this code in the appropriate
Body Diagnostic Manual and follow the flow chart
until the specific problem is located and resolved.
Once the problem is thought to be corrected, erase
the stored fault code using the DRB III
and verify correct system operation. If the front seat
heated seat system is functioning correctly, verify
that there are no other stored codes in the module
and return the vehicle to service.
If the fault code could not be verified, such as not
finding anything wrong when following the diagnos-
tic flow chart in the Body Diagnostic Manual. This is
a good indication that a INTERMITTENT problem
may be present. You must than attempt to find the
intermittent problem, such as moving the heating
element within the seat while testing continuity or
wiggling the wire harness's/electrical connectors
under the seat while testing continuity. Always, elim-
inate all other potential problems before attempting
to replace the memory heated seat adjustable pedal
module.
For complete circuit wiring diagrams, refer to Wir-
ing.
CS
scan tool
scan tool
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