Driver Seat Switch acting strange

bguzz · Post by **bguzz** » 16 Jul 2023, 20:00

2008 XC90 AWD 3.2

Drivers seat power works fine when using the seat switch. The memory does not seem to work. Pressing 1 was my wife's seat position and 2 was my seat position. Nothing happens when you hit the memory 1 or 2 now with the seat, but it remembers the side mirror positions and moves them to that every time.

Also, if the car is locked an my wife uses her key fob to unlock and then open the doors, it sometimes moves the seat to hear position 1 memory...same happens when I use my key fob to unlock and then open the door. Doesn't happen all the time though. There must be some sort of logic that I just don't get. So it seems the memory of our seat positions works, but using the switch doesn't.

Could that be the seat switch that is the problem?

Post by **xHeart** » 17 Jul 2023, 08:54

A quick search result https://volvo.custhelp.com/app/answers/ ... eat-memory

Post by **ggleavitt** » 17 Jul 2023, 13:29

Power Seat Module (PSM) is an active device, communicates with the CEM over LIN bus. Mirrors moving suggests the PSM to CEM to DDM path is working. No memory on the seat position might just be a corruption of some sort in the PSM itself, makes me wonder if you disconnected the battery for 30 minutes or so (allow vehicle to sit for 5 mins after running before pulling the battery connection to allow a write out to the modules) then reconnected, it might self-resolve.

Before you pull power though, doublecheck the wiring harness under the seat (from switch to motor). You have to cut the tie-wrap under the seat to replace the oft-broken modesty panel and if you don't reattach, it's possible that the harness gets caught in the seat and binds in the forward direction. While not your specific scenario, it's probably worth checking as part of your troubleshooting.

edit- probably worth, like moving forward vs backward.