This is a long bulletin. Hang tight for a couple of minutes, and I'll post it up here.

This bulletin is being revised to update the model year information. Please discard Corporate Bulletin Number 01-08-50-001B (Section 08-Body and Accessories)

Some customers may comment that the front/rear seat assembly heat function is not operating properly. The front/rear seat back and seat cushion remain cold when either the HEAT/OFF switch or the BACK ONLY switch is activated.

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

The heated seat system consists of four heated seats, two in the front and two in the rear. On the DHS and DTS models, each heated seat consists of four heat elements, one in the seat back and three in the seat cushion. On the DeVille model, each heated seat consists of two heat elements, one in the seat back and one in the seat cushion.

1. Determine which heat element is not functioning properly by measuring the resistance values of the factory heat elements. Refer to the appropriate diagnostic procedure in this bulletin.
2. If the resistance values of a factory heat element are NOT within the specified range, install a service heat element between the non-functioning factory heat element and the seat trim cover. Refer to the Service Heat Element Installation Procedure in this bulletin.

1. Adjust the front seat assembly to the maximum up and rearward position in order to access the seat cushion fasteners.




2. Remove the fasteners (1) retaining the seat cushion to the seat adjuster.
3. Disconnect the heated seat module harness blue, 8-way connector C2 (2).
4. Measure the front seat back element resistance between cavities G and H. Does the resistance measure less than 10 ohms?

•	If yes, go to Step 5.

•	If no, install a front seat back heat element. Refer to the Service Heat Element 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.

5. Measure the front seat back thermistor resistance between cavities E and F. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 6.

•	If no, install a front seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

6. Measure the front seat cushion thermistor resistance between cavities C and D. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 7.

•	If no, install a front seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

7. Measure the front seat cushion element resistance between cavities A and B. Does the resistance measure less than 10 ohms?

•	If yes, the resistance values of the front seat heat elements are within the specified range. To find the cause of the inoperative/cold heated seat, perform the standard diagnostic procedures in the Service Manual.

•	If no, go to Step 8 in order to determine which of the three seat cushion heat elements has a resistance value NOT within the specified range.

8. Remove the front seat assembly from the vehicle. Refer to Seat Replacement in the Seats sub-section of the Service Manual.
9. Remove the trim cover from the front seat cushion. Refer to Seat Cushion Cover Replacement -- Front in the Seats sub-section of the Service Manual.
10. Disconnect the green 2-way connectors between the seat cushion center heat element and the seat cushion thigh heat elements.
11. Measure the LH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector. Does the resistance measure less than 23 ohms?

•	If yes, go to Step 12.

•	If no, install a front seat cushion LH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

12. Measure the RH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector. Does the resistance measure less than 23 ohms?

•	If yes, install a front seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

•	If no, install a front seat cushion RH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

1. Adjust the front seat assembly to the maximum up and rearward position in order to access the seat cushion fasteners.




2. Remove the fasteners (1) retaining the seat cushion to the seat adjuster.
3. Disconnect the heated seat module harness blue, 8-way connector C2 (2).
4. Measure the front seat back element resistance between cavities G and H. Does the resistance measure less than 10 ohms?

•	If yes, go to Step 5.

•	If no, install a front seat back heat element. Refer to the Service Heat Element 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.

5. Measure the front seat back thermistor resistance between cavities E and F. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 6.

•	If no, install a front seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

6. Measure the front seat cushion thermistor resistance between cavities C and D. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 7.

•	If no, install a front seat cushion heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

7. Measure the front seat cushion element resistance between cavities A and B. Does the resistance measure less than 10 ohms?

•	If yes, the resistance values of the front seat heat elements are within the specified range. To find the cause of the inoperative/cold heated seat, perform the standard diagnostic procedures in the Service Manual.

•	If no, install a front seat cushion heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

1. Remove the rear seat cushion assembly (1) from the vehicle. Refer to Seat Cushion Replacement-Rear in the Seats sub-section of the Service Manual.

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.

2. At the rear seat cushion blue, 8-way connector C320 (2), measure the thermistor resistance.

•	For the LH rear seat cushion, measure between cavities C and D. Does the resistance measure between 280 ohms and 300 K ohms?

•	For the RH rear seat cushion, measure between cavities G and H. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 3.

•	If no, install a rear seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

3. At the rear seat cushion blue, 8-way connector C320 (2), measure the element resistance.

•	For the LH rear seat cushion, measure between cavities A and B. Does the resistance measure less than 10 ohms?

•	For the RH rear seat cushion, measure between cavities E and F. Does the resistance measure less than 10 ohms?

•	If yes, go to Step 8.

•	If no, for DeVille models ONLY, install a rear seat cushion heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

•	If no, for DHS & DTS models ONLY, go to Step 4 in order to determine which of the three rear seat cushion heat elements has a resistance value NOT within the specified range.

4. For DHS & DTS models ONLY: Remove the trim cover from the rear seat cushion. Refer to Seat Cushion Cover Replacement-Rear in the Seats sub-section of the Service Manual.
5. For DHS & DTS models ONLY: At the LH/RH rear seat cushion, disconnect the green 2-way connectors between the seat cushion center heat element and the seat cushion thigh heat elements.
6. For DHS & DTS models ONLY: Measure the LH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector. Does the resistance measure less than 30 ohms?

•	If yes, go to Step 7.

•	If no, install a rear seat cushion LH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

7. For DHS & DTS models ONLY: Measure the RH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector. Does the resistance measure less than 30 ohms?

•	If yes, install a rear seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

•	If no, install a rear seat cushion RH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

8. Remove the rear seat back assembly from the vehicle. Refer to Seat Back Replacement-Rear in the Seats sub-section of the Service Manual.




9. At the rear seat back LH (1) or RH (2) heated seat module, disconnect the blue, 8-way connector C2.

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.

10. Measure the rear seat back thermistor resistance between cavities E and F. Does the resistance measure between 280 ohms and 300 K ohms?

•	If yes, go to Step 11.

•	If no, install a rear seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

11. Measure the rear seat back element resistance between cavities G and H. Does the resistance measure less than 10 ohms?

•	If yes, the resistance values of the rear seat heat elements are within the specified range. To find the cause of the inoperative/cold heated seat, perform the standard diagnostic procedures in the Service Manual.

•	If no, install a rear seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.

If a sublet trim repair facility is used, please provide a copy of this bulletin to the repair shop.

Important: Before installing the service heat element to the seat trim cover, verify that the resistance values are within the correct range. Refer to the following table.

Important: DO NOT attempt to remove the factory heat elements from the seat trim cover. The service heat element is to be installed between the factory heat element and the seat trim cover.

1. Remove the trim cover with the non-functioning heat element. Refer to the appropriate seat trim cover removal procedure in the Seats sub-section of the Service Manual.
2. Place the seat trim cover on a clean flat surface with the inside facing out.

DHS/DTS and DeVille F/Seat (R/Seat Similar)






(1)	DHS/DTS F/Seat Back Trim Cover -- Inside Out
(2)	DHS/DTS F/Seat Cushion Trim Cover -- Inside Out
(3)	Cut-lines
(4)	Seat Cushion Wiring Harness Cut Locations
(5)	Seat Back Wiring Harness Cut Locations
(6)	DeVille F/Seat Cushion Trim Cover -- Inside Out
(7)	DeVille F/Seat Back Trim Cover -- Inside Out

3. Use a marker to draw in the cut-lines (3) on the non-functioning factory heat element. Refer to the appropriate illustration.
4. Remove the wiring harness from the non-functioning factory heat element.

4.1.	At locations (4) or (5), pull back the tape covering the harness wires.

4.2.	Use a pair of diagonal side cutters to cut the harness wires as close to the factory heat element material as possible.

DHS/DTS and DeVille F/Seat Back






Important: DO NOT start the cut with a jab or poke.

5. At the trim cover edge (2), using a razor blade or an equivalent sharp tool, slice through the factory heat element material along the cut-line until a hole is created.
6. Insert your finger(s) through the hole and lift the factory heat element material (1) away from the trim cover material.

Important: DO NOT cut through seams.

7. Using scissors and/or a razor blade, continue cutting the factory heat element material along the cut-lines.

DHS/DTS and DeVille F/Seat Back





8. Fold back the centers (1) of the factory heat element material. Insert the service heat element (2), with the backing paper side up, between the trim cover material and the factory heat element material.
9. Carefully remove the backing paper from the service heat element. Ensure the service heat element is laying flat.
10. Unfold the centers (1) of the factory heat element material.

DHS/DTS and DeVille F/Seat Back





11. Match the edges of the factory heat element material and cover the cut-lines with 3M® Highland^TM Cloth Duct Tape, P/N 6969, or equivalent. Ensure the service and factory heat elements are laying flat.
12. On DHS & DTS seat cushion installations: Connect the two thigh heat element electrical connectors to the center heat element.
13. Install the seat trim cover. Refer to the appropriate seat trim cover installation procedure in the Seats sub-section of the Service Manual.
14. On front seat assembly installations: Install the fasteners that retain the seat cushion to the seat adjuster.

Tighten
Tighten the fasteners to 9 N·m (80 lb in).

15. Place the seat assembly inside the vehicle. DO NOT install at this time.
16. Verify the seat heat function is operational.
17. Complete the seat assembly installation. Refer to the appropriate seat replacement procedure in the Seats sub-section of the Service Manual.

Parts Information

Model	Part Number	Description
FRONT
DeVille	25740850	F/Seat Back Cushion Heater
DHS & DTS	25715920
DeVille	25740851	F/Seat Cushion Heater
DHS & DTS	25715921
DHS & DTS	25715924	F/Seat Cushion (LH Thigh) Heater
DHS & DTS	25715925	F/Seat Cushion (RH Thigh) Heater
REAR
DeVille LH	25740852	R/Seat Back Cushion Heater
DeVille RH	25740853
DHS & DTS	25715926
DeVille LH	25740854	R/Seat Cushion Heater
DeVille RH	25740855
DHS & DTS	25715927
DHS & DTS	25715928	R/Seat Cushion (LH Thigh) Heater
DHS & DTS	25715929	R/Seat Cushion (RH Thigh) Heater

Parts are currently available from GMSPO.