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Wicked Wrench
Wicked Wrench, ASE/GM Master Certified 25Years
Category: Buick
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Experience:  GM Master Certified ASE Master Certified 25 Years Dealership Experience
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Buick LeSabre Custom: I recently purchased a 2004 Buick Lesabre

Resolved Question:

I recently purchased a 2004 Buick Lesabre Custom. I bought it to be a good used car for me that would last. It had about 120,000 miles on it but I like the 3.8 engine and it should last ok. Anyway, the heated leather seats on both the driver and passenger side are not working. Living in a cold climate, if I can fix it for a decent price it would be nice but I can live without it if it is costly.

I checked the fuses and they are ok. When you press the button to turn on the heat the HI light comes on but it takes many presses to get it to low or to turn off. Both sides are doing this. I don't know if this is a factor in the diagnosis but I found it odd so I included it.

I am trying to get a rough idea of what I'm looking at expense wise to see if it is worth taking to a dealer for diagnosis and fix. I don't think I would by handy enough to be doing any work myself inside the seat itself.
Submitted: 2 years ago.
Category: Buick
Expert:  Wicked Wrench replied 2 years ago.
When the light comes on, do the seats get warm?
Customer: replied 2 years ago.

No heat at all, the lights come on on both the driver and passenger side but nothing happens. Seats stay cold.

Expert:  Wicked Wrench replied 2 years ago.

Ok,

It sounds like more than just switches so let me do some poking around. Can I get back to you in an hour or so? Maybe less.

Expert:  Wicked Wrench replied 2 years ago.










Heated
Seats





HEATED SEATS DESCRIPTION AND OPERATION

The driver and front
passenger heated seats each consist of the following components.


  • Heated Seat Switch
  • Heated Seat Module
  • Seat
    Cushion
    Heater Element
  • Seat
    Back
    Heater Element
  • Temperature Sensor
  • HTDST LF Fuse 10 A
  • HTDST RF Fuse 10 A

The driver door module (DDM), passenger door
module
(PDM), and the rear integration module (RIM) are also involved in the
operation of the heated seats.

Power And Ground
Battery
positive voltage is supplied to both front heated seat modules from the rear
fuse block IGN 3 Fuse. This allows the heated seats to operate only when the
ignition in the ON position. Battery positive voltage is also supplied at all
times to the heated seat modules from the rear fuse block; HTDST LF Fuse for the
left heated seat module, or, HTDST RF for the right heated seat module. Both
modules are grounded through the module ground circuits to
G301.

Temperature Regulation
The heated seat system is
designed in order to warm the seat
cushion
and seat
back
to approximately 42°C (107.6°F) when in the high heat position,
and 37°C (98.6°F) when in the low heat position. The heated seat module
monitors the seat temperature through the temperature sensor signal circuit and
the temperature sensor (thermistor) that is located in the seat cushion. The
temperature sensor is a variable resistor, it's resistance changes as the
temperature of the seat changes. When the temperature sensor resistance
indicates to the heated seat module that the seat has reached the desired
temperature, the module opens the ground path of the seat heating elements
through the heated seat element control circuit. The module will then cycle the
element control circuit open and closed in order to maintain the desired
temperature.

Heated Seat Switch
The driver and passenger
heated seats are controlled by separate heated seat switches. Both heated seat
switches are grounded through a ground circuit provided by the associated door
control module. When the heated seat switch is pressed, the heated seat switch
signal circuit of the door control module is momentarily grounded indicating
either a high, low, or heat off command.

Heated Seat Operation

When the driver heated seat switch is pressed, the driver door module (DDM)
sends a class 2 message to the rear integration module (RIM) indicating the
driver heated seat command. In response to this signal, the RIM momentarily
sends a one shot pulse signal that is pulled low through the heated seat
high/low signal circuit to the heated seat module. The heated seat module then
applies or removes battery positive voltage through the element supply voltage
circuit to the seat heating elements.

When the passenger heated seat
switch is pressed, the passenger door
module
(PDM) sends a simple bus interface (SBI) message to the DDM
indicating the passenger heated seat command. The DDM then sends a class 2
message to the RIM indicating the passenger heated seat command. In response to
this signal, the RIM momentarily sends a 35 millisecond one shot pulse
signal that is pulled low through the heated seat high/low signal circuit to the
heated seat module. The heated seat module then applies or removes battery
positive voltage through the element supply voltage circuit to the seat heating
elements.

LED Temperature Indicators
When the heated seat is
off and the heated seat switch is pressed once, the heated seat module will set
the heated seat temperature to high heat. The door
module
then applies battery positive voltage through the high temperature
indicator control circuit to the heated seat switch illuminating the high
temperature indicator. When pressed again, the heated seat temperature is then
set to low heat and the door module applies battery positive voltage through the
low temperature indicator control circuit to the heated seat switch illuminating
the low temperature indicator. After a third press of the heated seat switch,
the door module removes battery positive voltage from the heated seat switch low
temperature indicator, and the heated seat module removes the battery voltage
from the seat heating elements. The heated seat module will also turn off the
heated seats whenever the ignition switch has been turned to the OFF
position.

Load Management
The ON/OFF status of the heated
seats is reported to the RIM through the status output signal circuit of each
heated seat module. During Load Shed Level 1, the RIM recognizes the heated seat
status signal as active, and will cycle the heated seat operation 16.0
seconds
ON and 4.0 seconds OFF. During Load Shed Level 2, the RIM
will signal the heated seat module to deactivate the heated seat operation, and
the door
modules
will turn off the appropriate heated seat switch temperature
indicators.


 

Expert:  Wicked Wrench replied 2 years ago.












Interior/A/C - Heated
Seats Inop. One Week After Repair





Bulletin No.: 05-08-50-003A

Date: December 13, 2005


TECHNICAL

Subject:
Heated Seat Inoperative After Repair Within One Week
of Usage (Replace Heated Seat Control Module)
Models:
2002-2005 Buick LeSabre
2003-2005 Cadillac CTS
2004-2005
Cadillac SRX
2005 Chevrolet Corvette
2002-2003 Oldsmobile
Aurora
2002-2005 Pontiac Bonneville

Supercede:


This bulletin is being revised to add models (2005 Chevrolet Corvette,
2002-2003 Oldsmobile Aurora) and remove the 2005 Cadillac STS. Please discard
Corporate Bulletin Number 05-08-50-003 (Section 08 - Body &
Accessories).


Condition


Some customers may comment that the heated seat function is inoperative
again, one week or less after repair for the same concern was completed. The
technician may have previously replaced the seat heater element and heated seat
control module assembly, and the new module may be inoperative.


Cause


Electrostatic discharge from the seat may cause the heated seat control
module to become inoperative.


Correction


Replace the heated seat module with the redesigned heated seat control module
assembly, P/N 10399538.





















Parts Information

Expert:  Wicked Wrench replied 2 years ago.












Interior - Front Heated
Seat Inoperative/Cold





Bulletin No.: 01-08-50-012B

Date: March 31, 2005


TECHNICAL

Subject:
Front Heated Seat Inoperative/Cold (Install Front
Seat Heater Package)
Models:
2000-2005 Buick LeSabre
2001-2003 Oldsmobile
Aurora
2000-2005 Pontiac Bonneville
with RPO KA1

Supercede:


This bulletin is being revised to update the model year information. Please
discard Corporate Bulletin Number 01-08-50-012A (Section 08-Body and
Accessories).

Important: This bulletin is being issued to inform the
technician that the Aurora Heater Package, P/N 25730798, is also to be used on
the 2003-2005 Bonnevilles that have leather front bucket seats (RPOs A51 - Front
Bucket Seat and IB2-Leather). The 2003-2005 Bonneville leather front bucket
seats share the same design as the Aurora front bucket seats.

Condition


Some customers may comment that the front seat assembly heat function is not
operating properly.


Cause


This condition may be due to a non-functioning heat element in the front
heated seat cushion or back trim cover.


Correction









1.Determine if the front seat assembly heat element resistance values are
within the specified range. Refer to the Diagnostic Procedure in this bulletin.
2.If the resistance values are NOT within the specified range, install a Front
Seat Heater Package between the existing front seat trim cover factory heat
elements and the seat
cushion
and back foam pads. Refer to the Front Seat Heater Package
Installation Procedure in this bulletin.

Diagnostic Procedure















1.Remove the front seat assembly from the vehicle. Refer to Seat
Replacement-Front Bucket/Split Bench in the Seats sub-section of the appropriate
Service Manual for the removal procedure.
2.Disconnect the heated seat module harness gray, 6-way connector C2.
3.Measure the seat heat element total resistance between cavities A and C.
Does the resistance measure less than 5 ohms?








^If yes, go to Step 4.
^If no, install the Front Seat Heater Package. Refer to the Front Seat Heater
Package Installation Procedure in this bulletin.
Important: If the resistance is measured
with the seat still warm, the resistance may vary outside of the specified range
since the thermistor resistance varies with temperature.
4.Measure the thermistor resistance between cavities D and F. Does the
resistance measure between 850 ohms and 11.50 K ohms?








^If yes, the resistance values of the heat elements are within the specified
range. To find the cause of the inoperative/cold heated seat, perform the
standard diagnostic procedures in the appropriate Service Manual.
^If no, install the Front Seat Heater Package. Refer to the Front Seat Heater
Package Installation Procedure in this bulletin.

Front Seat Heater Package Installation Procedure


























































































Prior to installation, connect all of the components (elements) of the Front
Seat Heater Package together and measure the resistance values. Refer to the
applicable illustration shown for element connection information.









^At the gray 6-way connector C2, between cavities A and C, the total
resistance of the service heat elements will be less than 5 ohms.
^At the gray 6-way connector C2, between cavities D and F, the thermistor
resistance of the service heat element will be between 850 ohms and 11.50 K
ohms.











1.Remove the seat
back
and seat
cushion
trim covers. Refer to the appropriate seat trim cover removal
procedures in the Seats sub-section of the appropriate Service Manual.
Important: DO NOT attempt to remove the factory heat elements from
the seat trim covers.
Important: ALL of the elements in the Front Seat Heater Package
MUST be installed in order for the system to function properly.
2.Remove the factory heat element wiring harnesses from the seat trim covers.
Use a pair of diagonal side cutters to cut the wiring as close to the factory
heat element as possible.
3.Install each of the service heat elements as follows:











3.1.Remove the backing paper.
3.2.Carefully position the service heat elements, harness side down, onto the seat
cushion
and back foam pads. For each seat cushion element, insert the
harness through a hole in the cushion foam pad.
3.3.Press the heat element onto the seat
cushion
and back foam pads. Ensure the heat elements are laying flat.

















































3.4.Connect the service heat element electrical connectors. Refer to the
applicable front seat cushion illustration for cushion heat element connection
information.

















4.Install the seat
back
and seat
cushion
trim covers. Refer to the appropriate seat trim cover installation
procedures in the Seats sub-section of the appropriate Service Manual.
5.Place the seat assembly inside the vehicle. DO NOT install the seat assembly
at this time.
6.Connect the seat assembly electrical connectors.
7.Verify that the seat heat function is operational.
8.Complete seat assembly installation. Refer to Seat Replacement-Front
Bucket/Split Bench in the Seats sub-section of the appropriate Service Manual
for installation procedures.

Parts Information




















Expert:  Wicked Wrench replied 2 years ago.

So, what I've provided for you here is a summary of how the system operates so you have an idea what is included in the system , & how it manages power.

The following two bulletins pertain to the two most common issues with these systems and they are the control modules, & the heater elements themselves. So you can see it is very important that you sit in BOTH seats & test the functionallity of them before condemming any parts. Now I will provide you with the diagnostic flow chart for the seat heaters. Do you have a scan tool & DVOM to measure voltage? If not, this job would best be suited for a Service Station that can perform these services.


Steps 1-3






Steps 4-7






Steps 8-11






Steps 12-15






Steps 16-21






Steps 22-28






Steps 29-35


The
numbers below refer to the step numbers on the diagnostic table.

 

  1. This step tests the integrity of the heated seat switch signal circuit of
    the driver door module. If the fuse in the jumper wire opens when you perform
    this test, the signal circuit is shorted to battery voltage.
  2. This step tests the integrity of the ground circuit of the heated seat
    switch.

 

  1. This step tests the integrity of the ground circuit of the heated seat
    module.

 

  1. This step tests the integrity of the heated seat High/Low signal from the
    rear integration module. This signal is a momentary 35 millisecond one
    shot pulse signal that is monitored through a momentary voltage change in the
    volt meter when the switch is pressed. In order to accurately recognize the
    change in voltage, the volt meter should stable before performing this
    test.
Wicked Wrench, ASE/GM Master Certified 25Years
Category: Buick
Satisfied Customers: 459
Experience: GM Master Certified ASE Master Certified 25 Years Dealership Experience
Wicked Wrench and 2 other Buick Specialists are ready to help you
Expert:  Wicked Wrench replied 2 years ago.
Hey Phil,
Just wondering how you've made out with the heated seats. Gimme a holler if you still need help, if not, please hit the "Excellent Service" icon on your screen if you haven't already, and thanks for using the site.

Happy Holidays!

W.W.

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