100 series BMW seat retrofit

[Martaigne]

Hey gang,

I'm working on retrofitting a pair of 2016 BMW 428xi sport seats into a 1998 LX470. I have a few diagrams, though some of the BMW diagrams I'm currently not 100% certain of having the right ones. I'm putting together information from various threads around the internet to try to figure out the wiring to have fully functioning power adjustable heated seats (because I have a fancy Toyota). I've found a workaround for the CANBUS signal on the seat modules to keep the power alive, using a 5v stepdown coupled with a 5sec timer. Please follow along while I most assuredly **** this up a few times before getting it right.

Links to some of the resources I'm using:

DIY: F32/F30 front electric seats install in E46 Coupe

Ever since sitting in my sisters F30, I loved the seats and thought it would be awesome to have them installed in my E46, which currently has E63 M6 seats i it, but the drivers seat foam is old and quite firm now. I like a challenge, but electronics and coding are not my thing, but i found a...

www.e46fanatics.com

Toyota-4Runner.org

The Largest 4Runner Community in the World

www.toyota-4runner.org

X4 Heated Seats Install!

X4 Heated Seats Install!

x3.xbimmers.com

LX470 heater wiring

LX470 control wiring

BMW heater wiring

BMW control wiring (may not be accurate for the model)

As best as I can tell, these are the wires I'm going to have to adapt/accommodate. The seat belt sensors are thankfully wired separately.

Driver BMW Seat:
Brown: Ground
Red: +12v 20a in (heater)
Red: Lumbar support
Red: +12v 30a in (controls)
Orange/green (CANBUS): wired to the 5s relay and 5v stepdown which gives it an intermittent signal to keep seat module alive
Green (CANBUS): not wired to anything?

Driver LX470 Chassis:
Thick Red: 12v+ 40a in (controls)
White/black: Ground
Blue/White: 12v+ 15a in (heater)

Passenger BMW Seat:
Brown: ground
Red: +12v 20a in (heater)
Red: Lumbar support
Red: +12v 30a in (controls)
Airbag Sensor Circuit?

Passenger LX470 Chassis:
Thick Red: 12v+ 40a in (controls)
White/black: Ground
Blue/White: 12v+ 15a in (heater)
Airbag Sensor Circuit?


From the above I'm guessing I'm going to have to create my own 20a power circuit for the BMW heaters as the 15a circuit and wiring from the LX470 won't be enough. I should be able to reuse and refuse the 40a circuit to provide the 30a power to the seats for the adjusters, however. In theory. I've already isolated the BMW seat air bag circuits and quarantined them to prevent accidental deployment.

Happy to hear feedback from anyone who may have more wiring expertise than I on this project.

 

[Martaigne]

After a little more scouring of the wires and diagrams, it appears as though the seat heaters are controlled by CANBUS signals in the BMW. So, I'll have to run a 20a wire to each seat, clip the brown and green paired wires coming out of the SCM (these are seat and seat back heater wires), and wire them into a relay controlled by the OEM Lexus switches. That will bypass the SCM for heater control but still allow the seats to be controlled by the SCM and switches off of the main seat adjuster power.

 

[AZSlim]

After a little more scouring of the wires and diagrams, it appears as though the seat heaters are controlled by CANBUS signals in the BMW. So, I'll have to run a 20a wire to each seat, clip the brown and green paired wires coming out of the SCM (these are seat and seat back heater wires), and wire them into a relay controlled by the OEM Lexus switches. That will bypass the SCM for heater control but still allow the seats to be controlled by the SCM and switches off of the main seat adjuster power.

What's the status? Any updates?

 

[Martaigne]

Slowly, but surely. I'm going to be using a 5v timer relay to spoof the CANBUS signal to the seat controller via the green/orange wires to prevent it from powering off.

I had a friend 3d print some housings for this controller, and as it's only a 5v draw, I am also wiring in a 12v=>5v stepdown converter to reduce the voltage and preserve the controller relay.

Right now I'm researching how to mount the seats physically. I'm looking at the Planted seat brackets because I suspect the BMW seats will bolt directly to them. Once I make that call, I'll have a bit more to show.

 

[FxFormat]

Interesting project, ive driven hundreds of different types of cars/trucks while at my shop. The most comfortable seat for me is from a 2013+ LS460, it's just the right about of plush, support, and size. If i were to retrofit that's what i would choose. Now you got me thinking of doing it.