[trjn]

2015 535i xdrive
napa comfort heated seats

I bought this car a couple of months ago knowing the driver's seat electronics didnt work. I thought it would be an easy fix with the change in either fuses, switch or module.

Current situation:
Memory works(mirror and steering wheel)
Heat works.
Lumbar support buttons work.

But other seat adjustment buttons do not do anything.

Troubleshooting steps:

- Changed all the fuses that are labelled for seats. No go.
- scanning with ISTA gives SMFA error, which points to module or switch error.
However, I can access all the seat movements from ISTA commands. ISTA also recognizes all the seat adjustment buttons when activated. I set the seat to position to my liking via ISTA.
- Bought a used driver's seat switch assembly, same issue. Lumbar support buttons work, but not the other buttons.

From studying the diagrams in TIS, I feel its the issue is either with the wiring or the seat module.
I doubt its a wiring issue because I can use ISTA to access all the motors and also ISTA reads the buttons when activated even though there is no movement of seats via button presses. But who knows.

For who have experienced such issue or did a seats retrofit, what would a logical next step?
Just change the seat module with a new/used one or try and trace the wiring to LIN bus?

Its my 4th BMW and have done a ton of retrofits in my BMWs and previous audi including changing individual seat motors and wiring to install memory seats in that car. So, I am pretty confident on doing the wiring, but would want an insight on what should be my next step.