2002 envoy heated seats won't turn off, suggestions?

Heated Seat System Operation
The driver and passenger heated seats have 2 heat zone operating modes with 3 heat level modes and will operate only while the engine is running. The heat zones are determined by which of the 2 heated seat buttons are pressed, while the heat level is determined by the number of times they are pressed. Pressing the seat cushion button 1 time will activate the seat back and cushion heater elements in the high mode. Each time the seat cushion button is pressed the seat back and cushion heat level is reduced from high to medium, low, and off. Pressing the heated seat back button 1 time will activate only the seat back heater element in the high mode. Each time the seat back button is pressed the seat back heat level is reduced from high to medium, low, and off. During heated seat operation the heat zone operating mode may be changed without affecting the current heat level mode.
The heated seat switches are momentary contact switches and are inputs to the driver and passenger door modules. Battery voltage is supplied to the switch assembly from the door module, and when a heated seat switch is pressed and released a brief switch signal voltage is supplied to the door module. Whenever the door module receives an active heated seat switch input, the next heated seat operating mode is determined by whatever the current mode may be. The seat heater elements are controlled by the driver seat module using inputs from the door modules through Class 2 serial data circuit messages. The driver seat module controls the voltage supply and the ground circuits to the seat heater elements. When a heated seat function is commanded active, the seat module will switch battery voltage to the heater element supply circuits, and ground is provided through low side drive control circuits. During heated seat operation both the seat back and cushion heater elements are supplied battery voltage. The seat module grounds the appropriate control circuits for back only or back and cushion heating modes, and opens or closes the active control circuits as necessary in order to maintain the desired seat temperature. The seat module relies on inputs from thermistors located in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and a low reference circuit from the seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise. The seat modules allow heated seat operation only while the engine is running which is determined by a Class 2 serial data circuit message from the powertrain control module.

Heated Seat Components
The heated seat system consists of the following components:
• Driver and passenger heated seat switches
• Driver and passenger seat back heater elements
• Driver and passenger seat cushion heater elements
• Driver and passenger seat back temperature sensors
• Driver seat module
• Driver door module
• Passenger door module

Do you know what B - body DTC -diagnostic trouble code are ?
DTC B2425 Driver Seat Heater Circuit
DTC B2435 Driver Seat Back Heater Sensor Circuit
DTC B3941 Front Seat Heaters Circuit

Heated Seat Always On
Step
Action
Yes
No
Schematic Reference: Driver Seat Schematics and Passenger Seat Schematics
Connector End View Reference: Power Seat Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Operate the heated seat system.
Does the system operate normally?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Install a scan tool.
Display the Heated Seat Status parameter in the driver seat module Input/Output data list.
Start the engine.
Does the scan tool display the Heated Seat Status parameter as Off?
Go to Step 6
Go to Step 4
4
Display the Heated Seat Mode parameter in the door module Inputs data list.
Does the scan tool display the Heated Seat Mode parameter as OFF?
Go to Step 6
Go to Step 5
5
Turn OFF the ignition.
Disconnect the heated seat switch connector to the door module.
Start the engine.
Does the scan tool display the Heated Seat Mode parameter as OFF?
Go to Step 7
Go to Step 8
6
Replace the driver seat module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the repair complete?
Go to Step 9
--
7
Replace the heated seat switch. Refer to Front Seat Heater Switch Replacement .
Is the repair complete?
Go to Step 9
--
8
Replace the door module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the repair complete?
Go to Step 9
--
9
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3


your best bet , have a qualified repair shop diagnose the problem

Not a fuse issue , more then likely a burnt heating element in the seat , happens all the time .
Heated Seat Components
The heated seat system consists of the following components:
• Driver and passenger heated seat switches
• Driver and passenger seat back heater elements
• Driver and passenger seat cushion heater elements
• Driver and passenger seat back temperature sensors
• Driver seat module
• Driver door module
• Passenger door module

The control module have a Battery voltage supply , the module supply's voltage to the seat heating elements .
The heated seat switches are momentary contact switches and are inputs to the driver and passenger door modules. Battery voltage is supplied to the switch assembly from the door module, and when a heated seat switch is pressed and released a brief switch signal voltage is supplied to the door module. Whenever the door module receives an active heated seat switch input, the next heated seat operating mode is determined by whatever the current mode may be. The seat heater elements are controlled by the driver seat module using inputs from the door modules through Class 2 serial data circuit messages. The driver seat module controls the voltage supply and the ground circuits to the seat heater elements. When a heated seat function is commanded active, the seat module will switch battery voltage to the heater element supply circuits, and ground is provided through low side drive control circuits. During heated seat operation both the seat back and cushion heater elements are supplied battery voltage. The seat module grounds the appropriate control circuits for back only or back and cushion heating modes, and opens or closes the active control circuits as necessary in order to maintain the desired seat temperature. The seat module relies on inputs from thermistors located in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and a low reference circuit from the seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise. The seat modules allow heated seat operation only while the engine is running which is determined by a Class 2 serial data circuit message from the powertrain control module.

Your best bet , take it to a qualified repair shop.

?€¢
DTC B2430 Passenger Seat Heater Circuit

Do you know what DTC'S - diagnostic trouble code's are ?

The driver and passenger seat heaters are controlled by the driver seat module. Power is supplied to the driver seat cushion and back heater elements through individual voltage supply circuits. Power is supplied to the passenger seat cushion and back heater elements through a common voltage supply circuit. All of the driver and passenger seat heater elements are grounded by the driver seat module through individual low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the driver seat module in order to control the seat temperatures by regulating the current flow through the heater elements.
Your best bet , take it to a qualified repair shop that has diagnostic scanner that can read this code's

?€¢
DTC B2430 Passenger Seat Heater Circuit

Do you know what DTC'S - diagnostic trouble code's are ?

?€¢
DTC B2435 Driver Seat Back Heater Sensor Circuit

?€¢
DTC B2440 Passenger Seat Back Heater Sensor Circuit

The driver seat module relies on inputs from thermistors installed in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2-wire sensors supplied with a 5-volt referenced signal circuit and low reference circuit from the driver seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise.

Not a fuse problem , more likely a burnt out element .
CHEVY GMC SEAT HEATER TROUBLESHOOTING YouTube

Your best bet , take it to a qualified repair shop.

The heated seat system consists of the following components:
• Driver and passenger heated seat switches
• Driver and passenger seat back heater elements
• Driver and passenger seat cushion heater elements
• Driver and passenger seat back temperature sensors
• Driver seat module
• Driver door module
• Passenger door module

Do you know what a electronic module is ?
DTC B2425 or B2430
Circuit Description
The driver and passenger seat heaters are controlled by the driver seat module. Power is supplied to the driver seat cushion and back heater elements through individual voltage supply circuits. Power is supplied to the passenger seat cushion and back heater elements through a common voltage supply circuit. All of the driver and passenger seat heater elements are grounded by the driver seat module through individual low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the driver seat module in order to control the seat temperatures by regulating the current flow through the heater elements.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC B2425 Driver Seat Heater Circuit
• DTC B2430 Passenger Seat Heater Circuit

Do you know what a DTC - diagnostic trouble code is.

Heated Seat Components
The heated seat system consists of the following components:
• Driver and passenger heated seat switches
• Driver and passenger seat back heater elements
• Driver and passenger seat cushion heater elements
• Driver and passenger seat back temperature sensors
• Driver seat module
• Driver door module
• Passenger door module
When there are modules involved in the operation of any componet that's acting up , the module's electronic's could be the culprit ! But without testing who's to say what the problem could be !
I would have it check for DTC'S
DTC B2425 or B2430
The driver and passenger seat heaters are controlled by the driver seat module. Power is supplied to the driver seat cushion and back heater elements through individual voltage supply circuits. Power is supplied to the passenger seat cushion and back heater elements through a common voltage supply circuit. All of the driver and passenger seat heater elements are grounded by the driver seat module through individual low side drive control circuits. The heater element control circuits are pulse width modulated to ground by the driver seat module in order to control the seat temperatures by regulating the current flow through the heater elements.
DTC B2435 or B2440
The driver seat module relies on inputs from thermistors installed in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2-wire sensors supplied with a 5-volt referenced signal circuit and low reference circuit from the driver seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise.
Install a scan tool.
Start the engine.
Turn the heated seat ON.
With a scan tool, observe the Heated Seat Sensor parameter in the data list for the driver seat module.
Does the scan tool indicate that the heated seat sensor parameter is within the specified range?
0.078-4.94 V

have you tried replacing the fuse and also looking at the connections under the seat

If your vehicle is equipped with heated seat, there should be a control button on the door where the window buttons are.

In attached figure, item #15 is control module for seat heater and is located under passenger seat.

When this was happening on my Envoy it ended up being the seat heaters control module that was going out. About $600 a seat on mine. Just wish my repair center found that out before they replaced the seat heaters twice.