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Intermittent heated seats on GM SUVs

Service bulletin Intermittent heated seats on GM SUVs

GM has issued a service bulletin 05-08-50-008 to address intermittent heated seats on GM SUVs which are listed below. The service bulletin covers several fixes for intermittent heat seats that don’t operate when activated, heated seats shut off early or heated seats turn on by themselves.

Heated seats don’t turn on

In the heated seats don’t turn on scenario, the driver can push the heated seats button and the heaters will not come on. But if the driver turns the key to OFF and then back to ON, they will work. Other times, the heated seats will turn on normally. So the problem is intermittent heated seats that may include trouble code B3941.

B3941 front seat heaters circuit

The B3941 front seat heaters circuit trouble code sets with the driver’s door module (DDM) or passenger door module (PDM) detects that the voltage to the seat heater element is shorted to ground.

Power is supplied to the seat heater elements by the door modules. Ground for the heater elements is pulse width modulated so the module can vary the on/off time of the circuit and thereby adjust the heat. The door modules also monitor temperature to shut down the system in the event of overheating.

Heated seats turn off early

In other cases on some LB7 diesel engine vehicles, the driver can request heated seats and they turn off during the first 10 minutes. However, this only happens on the first seat heat request of the day. After that, on additional trips, the seat heater will come on and stay on as normal. Or, the problem may occur intermittently. These conditions are intermittent and DTC B3941 may be set.

Heated seats turn on by themselves

In this case, the driver experiences intermittent heated seats even though they may not have requested them by pushing the button.

Vehicles Affected by 05-08-50-008

2003-2005 Cadillac Escalade, Escalade ESV, Escalade EXT
2003-2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003-2005 GMC Sierra, Yukon, Yukon XL, Yukon Denali; All with Seat FRT, Individual (Non BKT) (RPO AN3)
2003-2005 HUMMER H2 with Seat, Front Bucket Deluxe (RPO AR9)

Diagnose the problem

This is a tough one for DIYers since accurate diagnosis requires a high end scan tool to poll the door modules to see if it is commanding the heaters on or off based on the seat heater switch operation. However, there are some tests DIYers can do with a voltmeter

First, get a wiring diagram and specifications from a heated seat moduleshop manual. Test the seat heater switches to make sure they are not shorted. Next, check the heater element resistance values to make sure they’re within specification and not shorted. If everything checks out, chances are you’ve got to reprogram the door module in question or replace it. But don’t go out and buy a door module, because it has to be programmed FOR YOUR EXACT VIN.

The driver’s door module is in the door behind the trim panel

Reprogramming the driver’s door module

For more information on reprogramming, see this post

Any shop that has reprogramming capabilities can reprogram a door module and many times reprogramming with the latest software will solve the problem. If it doesn’t you’ll have to replace the door module with a fully programmed unit.

©, 2018 Rick Muscoplat

Posted on by Rick Muscoplat

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