Passenger and driver heated seats do not work.

The heated seats are a luxury feature that heat the front seats. This provides maximum comfort for the driver and the front passenger. To turn on the heated seats, press the heated seat button, which is a picture of a seat. There are two of these buttons, and each are located on the center console. The button on the driver's side of the console controls the heat for the driver's seat, while the button on the passenger's side of the center console controls the heat for the passenger's seat. Pressing the heated seat button will turn the heated-seats onto their highest setting. Pressing the button a second time will lower the heated seats to their medium setting. Pressing the button a third time will result in the lowest setting. Pressing the button a fourth time will turn off the heated seats. There are three lights next to the heated seat buttons to indicate what setting the heated seats are on.
Tip
The heated seats will only work when the engine is running.

Check your connections going to seats

check fuses first

Remove the ignition key. Unplug the HSM (heated seat module). It is under the passenger seat. You can easily accomplish this with the seat all the way back. Wait a few seconds they plug it back in. Start the engine. Turn the seats on. If the indicator lights come on for 2 seconds and then go out, further diagnostics is required. Hopefully they'll stay on and the seats will be working fine.

Thanks,
Ron

sound like a relay / turn off anything that makes noise and in the quite listen for a clicking noise when you push the button. Could be located under the hood on the drivers side or under the seats

Would you say it stays on about 30 seconds and does the passenger side do the same thing? If possible retrieving the codes will narrow down the search for a correct solution.If the passenger side is ok we may be able to eliminate the passenger side as bring part of the problem.Please advise so will know which way to go with your solution.


Condition/Concern: Driver and passenger heated seats inoperative or shut off in 30 seconds. There will be DTCs B2435, B2440, B3606 and/or B1825 set in the Drivers Seat Module. The adjustable pedal position sensor, seat recliner position sensor and both heat seat thermistors share the same 5 volt reference internal to the Drivers Seat Module. A fault in any of these components/circuits can make the heated seats inoperative or shut off in 30 seconds, as well as, the seat recliner and/or adjustment pedals may move in short increments when operated. A fault in heated seats, adjustable pedal or seat recliner will affect BOTH heated seats.
Note:: Even if the vehicle is not equipped with adjustable pedals DTC B3606 still may set.


To help isolate the area of concern use the Tech 2 or a comparable scanner and go to "Sensor Data" in the Drivers Seat Module. Monitor the following parameters for being out of range:
Recline Position- Normal range .39V-4.58V
Pedal Position (if equipped) - Normal range .39V-4.58V
Psgr. Seat Heat Sensor- Normal range 1V-4V
Drvr. Seat Heat Sensor- Normal range 1V-4V
If a parameter is found to be out of range inspect circuits for any opens, shorts to ground, or voltage. If none found replace the suspect component.

Please be aware of the following common areas of concern:

1. The adjustable pedal position sensor internally shorted pulling the 5 volt reference low. Disconnect the adjustable pedal position sensor and see if the heated seats start working correctly, if so replace. Note Important:: The APP (Accelerator Pedal Position) sensor is NOT the adjustable pedal position sensor. Make sure the correct sensor, adjustable pedal position sensor, is disconnected.
   
2. The seat recliner position sensor internally shorted pulling the 5 volt reference low. Disconnect the recliner position sensor and see if heated seats start working correctly, if so replace.
3. An open in either heated seat thermistor circuits (signal or low reference). The most common is the passenger thermistor where it passes through seat connector C305 pin "L" or "K" or C399 pins "R" or "G".
4. A chaff to ground on either heated seat thermistor signal circuits. The most common is circuit 5475 black/red or dark blue shorted to ground in the passenger seat near the buckle. Note Important:: The heated seat thermistors act differently to "OPENS and SHORTS" than the adjustable pedal position sensor and seat recliner position sensor. The adjustable pedals and seat recliner sensors can be disconnected for testing of the heated seats. Where as the heated seat thermistor circuit must be working correctly before EITHER heated seat will operate. Disconnecting one thermistor, which may have a concern will not allow the opposite heated seat to work correctly, BOTH side must be operational before EITHER heated seat will operate.
   

Clearing DTCs
If DTCs will not clear when using the Tech 2 or comaparable scanner after a repair has been made, try operating the device in which the repair was made. Example, if a repair was made to the passenger heated seat thermistor circuit, the DTCs may not clear unless the passenger heated seat is operated.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Mine did that forever, but started working after the instrument cluster was replaced. It started to show 100 mph in a parking lot. Dealer replaced it for free, and now every little quirk seems to have disappeared, including the heated seats. They are very nice lately. Damn cold here.

This is usually a problem with the passenger seat heater control module. It is a common failure on your vehicle. The module is part of the seat cushion.

Just for the heck of it though, check to make sure the wiring to the module under the seat is connected and not loose.

The body control module in this vehicle sees a short in the seat heater system. These vehiucles are typical of the heater wiring shorting out. When you try to use the bad heater the computer shuts off all the heaters.

You will need to install a new seat heater pad.

Identical thing here with my '03 Surburban LT.