Powered seat blown fuse - now dead

tiwillia · March 23, 2020

Last week I noticed my passenger side powered seat on my 2017 Sierra Denali was no longer working. Just dead, switches resulted in no movement.

Checked the fuse and it was blown, replaced with a spare and tried the seat again.

Lower seat switch worked fine. Seat back switch worked fine. The moment I moved the lumbar support switch I saw a flash come from underneath the seat and the fuse was blown.

I replaced the fuse again and - nothing. The seat is now dead. The driver's seat makes a sound like a relay switching when you move the switches, but I don't even get that on the passenger seat now. Verified again that the fuse is fine, moved it to the rear sliding glass to test.

Anyone have any idea what may have broken? I understand it appears I have/had a short somewhere in the lumbar support, but now the whole passenger seat seems to be dead. Is there a relay somewhere that would need to be replaced? Anyone have the powered seat wiring diagrams?

Would anyone, at minimum, be able to remove their passenger side seat fuse and tell me if they hear the relay switching noise even when the fuse is removed?

First post since I've always been able to find the answer here before with some creative searching, but not this time.

Lsgun1 · March 24, 2020

Look under the seat, wires may have been squished causing the short to ground/power which is why the fuse blows right away.

tiwillia · March 24, 2020

Yeah I took off the seat plastic that just clips in and had a really good look under there. I unzipped the back too and looked around at the lumbar bag and the wires around it.

As far as I can tell, I can't see any electrical burn marks, any crushed wires, or any wire insulation that has been stripped away.

Next step is to try to figure out how to get the plastic behind the switches off and get a better look at the wiring for the switches themselves. Really wish I had a service manual.

Lsgun1 · March 25, 2020

You can unbolt the whole seat from the floor and tip it back to see most items under there.

JimCost2014 · March 25, 2020

On 3/24/2020 at 6:21 AM, tiwillia said:

Yeah I took off the seat plastic that just clips in and had a really good look under there. I unzipped the back too and looked around at the lumbar bag and the wires around it.

As far as I can tell, I can't see any electrical burn marks, any crushed wires, or any wire insulation that has been stripped away.

Next step is to try to figure out how to get the plastic behind the switches off and get a better look at the wiring for the switches themselves. Really wish I had a service manual.

Maybe your module is going bad? Module - GM (23192138)

tiwillia · March 26, 2020

1 hour ago, JimCost2014 said:

Maybe your module is going bad? Module - GM (23192138)

Thanks for the part number, its good to know its only a $40 part.

Taking it to the dealership tomorrow to let them diagnose, if its just the module I'll replace myself.

JimCost2014 · March 26, 2020

5 minutes ago, tiwillia said:

Thanks for the part number, its good to know its only a $40 part.

Taking it to the dealership tomorrow to let them diagnose, if its just the module I'll replace myself.

You are very welcome.

Good luck!

tiwillia · March 27, 2020

Dealer identified a cable was cut between the module and the switch. Module has power but the wires going into the switch don't.

They wanted $700 to fix it, so I'll be taking the seat out myself and removing/inspecting the harness they mentioned.

Now to search for the diagram for circuit 1440...

Sent from my Pixel 3 XL using Tapatalk

JimCost2014 · March 29, 2020

On 3/27/2020 at 4:58 AM, tiwillia said:

Dealer identified a cable was cut between the module and the switch. Module has power but the wires going into the switch don't.

They wanted $700 to fix it, so I'll be taking the seat out myself and removing/inspecting the harness they mentioned.

Now to search for the diagram for circuit 1440...

Sent from my Pixel 3 XL using Tapatalk

Did they offer any info on how the cable could have been cut?

Possibly the way the seat was installed from the factory, if so I would go after a warranty repair.

tiwillia · March 31, 2020

On 3/28/2020 at 9:30 PM, JimCost2014 said:

Did they offer any info on how the cable could have been cut?

Possibly the way the seat was installed from the factory, if so I would go after a warranty repair.

They did not offer any further info, no.

I'm at 42k miles, so out of factory bumper-to-bumper warranty.

JimCost2014 · March 31, 2020

31 minutes ago, tiwillia said:

They did not offer any further info, no.

I'm at 42k miles, so out of factory bumper-to-bumper warranty.

This just sounds suspicious on how the cable was cut.

I would open a claim with GM to see if they will cover the full, or partial cost of the repair.

They may help, probably will if you have a good relationship with the dealership.

Can you provide any photos of what they are describing?

tiwillia · April 2, 2020

Apparently there is a circuit breaker in the seat circuit somewhere. If you unplug the seat (with the big plug underneath the plastic below the seat switch panel) for a few minutes and plug it back in, it resets the circuit breaker.

So I was able to get power back to the seat to move it so I could access the bolts (remember the horizontal movement still works, the lumbar is where the short is).

I removed the seat complety, took a lot of it apart, inspected every connector associated with the lumbar I could find, and finally found the short near the connector to the switch panel. You can see the corrosion and the exposed wire on the bottom-most wire in this picture:

tiwillia · April 2, 2020

Here is my fix. Taped up the exposed wire real well with electrical tape. The rest of the wires had scratches on the insulation, so they were at risk of this too, so I taped each one, then taped them all together with several layers of tape.

Wire-tied them to the switch panel plastic and they are no longer rubbing on that rusty looking metal piece.

Seat is back in and working great now.

Thanks for all the help.

JimCost2014 · April 2, 2020

1 hour ago, tiwillia said:

Here is my fix. Taped up the exposed wire real well with electrical tape. The rest of the wires had scratches on the insulation, so they were at risk of this too, so I taped each one, then taped them all together with several layers of tape.

Wire-tied them to the switch panel plastic and they are no longer rubbing on that rusty looking metal piece.

Seat is back in and working great now.

Thanks for all the help.

Nice work.

Do you have a lot of "rusty" metal under the seats?

tiwillia · April 2, 2020

8 minutes ago, JimCost2014 said:

Nice work.

Do you have a lot of "rusty" metal under the seats?

No, just that one piece. If you look under your seat, its a long metal rod that goes from one side of the seat to the other in the front. It holds on the plastic that keeps a lot of the wires from falling down or getting caught.

It also seems to provide rigidity to the seat. Its just got surface rust on it, doesn't seem to be an issue. GM painted every piece of metal under the seat except that one rod.