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2009 STS
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29 Posts
Discussion Starter #1
Hello all, I have a 2009 STS and the driver's lumbar stopped working which leaves a depression in the seat back that makes it very uncomfortable to drive for any length of time.

I took the seat back off and found the mechanism that moves the lumbar had come apart with the one motor whirring but not moving, so I presume the gears are stripped, so I'd like to replace the mechanism. Looking online I can buy the part from GM, part #88992732 for about $135, but what I don't know is the difficulty level of replacing the mechanism. The part is pre-assembled and appears like it will plug in, but I've tried and don't see how to get the old part out of the seat.

Has anyone had any experience with this and can give some pointers? I've got some mechanical skills but it always helps to have a detailed diagram or instructions to work from.

If I can't get the old one out I may just put a piece of hard foam or rubber in to give at least some lumbar support and close it back up.

Any ideas or help will be very much appreciated!
 

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2015 SRX LUX 2014 CTS LUX Phantom Grey (previously 2008 STS)
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1,707 Posts
I may just put a piece of hard foam or rubber in to give at least some lumbar support and close it back up.

Any ideas or help will be very much appreciated!
That's what I would do on a 11 year old vehicle. I had mine replaced on my 2008 but that was under warranty
 

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2006 STS4 4.6L
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422 Posts
They use these plastic or nylon type gears in basically all the adjusters which break over time, it's pretty annoying but not surprising. That circular black plastic piece on the right side is where the gears are, I would honestly rather just change that out than the while mechanism. I've messed around with pretty much all the adjusters in the seat, it isn't too difficult. Pull the panel off the back of the seat and take a gander, it's been a couple years since I messed with it.
 

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96 STS; 09 STS4 N* Platinum w/1SG & PCZ
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178 Posts
There was a post a while back about replacing the lumbar motor. I can't remember if it was here or on YouTube. Do a quick search. It was a pretty detailed tutorial.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Looking at the service manual, you need to remove the rear seat panel (as you did), headrest, headrest guides, speaker grilles (if applicable), seat cover (leather) and the seat back foam. You can probably get away with only pulling the seat leather down from the top but likely not all the way off. Once you've goccess, disconnect all the (necessary) electrical connectors.

Once this is all out of the way, you will pull the lumbar assembly forward (toward the steering wheel) at the bottom to disengage it from the retainers. Lastly, pull the assembly downward to disengage it at the top and remove it from the seat. It comes out from the front.

There 'may' be a less complicated way to do this. I'm just relaying what's in the service manual. I plan to do mine as well. The assembly works, but the position sensor is intermittent so I want to service it for that reason. I'm hoping in my case that I'll be able to swap the motor and sensor from one assembly to the other.
 

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2006 STS4 4.6L
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422 Posts
I seriously doubt you need to replace the motor, I'll bet you it's those gears in there. Open the little gear mechanism up and take a look. I bet one or two of those gears are either missing some teeth or are totally disintegrated.
 

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2009 STS
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29 Posts
Discussion Starter #8
There was a post a while back about replacing the lumbar motor. I can't remember if it was here or on YouTube. Do a quick search. It was a pretty detailed tutorial.
Yes, saw that video and this may be something we work on if the pad we stuffed in the seat is not adequate. Thanks for your help!
 

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2009 STS
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29 Posts
Discussion Starter #9
Looking at the service manual, you need to remove the rear seat panel (as you did), headrest, headrest guides, speaker grilles (if applicable), seat cover (leather) and the seat back foam. You can probably get away with only pulling the seat leather down from the top but likely not all the way off. Once you've goccess, disconnect all the (necessary) electrical connectors.

Once this is all out of the way, you will pull the lumbar assembly forward (toward the steering wheel) at the bottom to disengage it from the retainers. Lastly, pull the assembly downward to disengage it at the top and remove it from the seat. It comes out from the front.

There 'may' be a less complicated way to do this. I'm just relaying what's in the service manual. I plan to do mine as well. The assembly works, but the position sensor is intermittent so I want to service it for that reason. I'm hoping in my case that I'll be able to swap the motor and sensor from one assembly to the other.
Thanks, but with the age and mileage (106K) I'm thinking we're not going to make this amount of effort. We really appreciate you posting to let us know what needs to be done as this was amazingly helpful!
 

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2009 STS
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29 Posts
Discussion Starter #10
I seriously doubt you need to replace the motor, I'll bet you it's those gears in there. Open the little gear mechanism up and take a look. I bet one or two of those gears are either missing some teeth or are totally disintegrated.
Thanks, we'll see if we want to do this!
 

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2015 SRX LUX 2014 CTS LUX Phantom Grey (previously 2008 STS)
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1,707 Posts
On my lumbar supports I just set and forget. Rarely, if ever adjust
 

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2009 STS
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29 Posts
Discussion Starter #12
On my lumbar supports I just set and forget. Rarely, if ever adjust
My wife and I both drive this car at times, and she is much smaller than I am so the seats do adjust based on the driver. One of the cool things about this car we like. But, I think the lumbar doesn't have to be changed and cannot be unless we decide to change out the gear set as suggested above, which we are thinking about. Thanks again and this group has been most helpful!
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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3,205 Posts
The only reason I suggest replacing the entire mechanism is that if you've got some stripped gears, there's also the possibility for other wear in the mechanism. Swapping gears may be fine, but you may be back in there again later for other maintenance. There's two motors (up/down, in/out). If you could just buy the part(s) you needed, that would be one thing. Since you already have the whole assembly, it's your time. Just my two cents worth.
 
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