E46 Convertible & E93 Seat Looms Translated Into Layman's English

[Headloch]

Long time lurker, first time poster. I'm going to list the wire colours in the seat harnesses for 2003 E46 and then 2009 E93 and relate their purpose. I have had a very hard time finding this information and spent hours trawling through the (German) wiring diagrams to understand what is going on for a retrofit of heated E93 M3 seats into an E46 convertible - yes it can be done, despite the difficulties others have faced! I'll do a write-up when finished. If you are wondering, hall sensors are used to detect movement using magnets and are essential for seat memory functions. Anyway, here you go:

Important: Depending on the year of your seats, you may have different wire colours, particularly with the E93. Most will match, but do not be surprised to find minor discrepancies.

E46

Forward/backward seat adjustment
green/white = hall sensor -
green/brown = hall sensor +
black/yellow = motor +
green/yellow = motor -
yellow/red = comfort + (increased motor speed)

(not 100% confident in the motor labels, but it works so who cares!)

Seat height adjustment
purple/grey = motor +
blue/red = motor -

Backrest angle adjustment*
black/purple = motor -
green/purple = motor +

Seat tilt adjustment
blue/red = motor -
purple/red = motor +

Headrest up/down adjustment
blue/white = hall sensor -
green/red = hall sensor +
green/yellow = motor +
red/white = motor -

Heating (Passenger)
green/yellow = filament +
white/blue = setting (connects to a variable resistor in the seat to change the temperature between 3 options)
brown = filament -

Heating (Driver)
green/purple = filament +
white/green = setting (connects to a variable resistor in the seat to change the temperature between 3 options)
brown = filament -

Backrest Switch (activates if the seat is folded down)
grey/black = +
grey/white = -

Comfort Buttons (on top of the seat for double speed)
yellow = forward
black = ground
white = backward

Miscellaneous
red/white with yellow dots = K-CAN (relays information with the car such as "door open" using a bus network)
blue/black with yellowdots = bus to instrument cluster, I believe for backrest folding. Labelled as seatbelt buckle, but convertible doesn't have sensors in the buckle.


E93

Forward/backward seat adjustment
brown/purple = hall sensor -
purple/black = hall sensor +
yellow = motor -
blue = motor +
purple = comfort + (increased motor speed)

Seat height adjustment
white/black = hall sensor -
red/white = hall sensor +
white/green = motor -
brown/white = motor +

Backrest angle adjustment
purple/brown = hall sensor -
purple/black = hall sensor +
green/purple = motor -
black/purple = motor +

Seat tilt adjustment
blue/green = hall sensor -
red/blue = hall sensor +
blue/black = motor -
brown/blue = motor +

Headrest up/down adjustment
blue/white = hall sensor -
green/red = hall sensor +
red/white = motor -
green/yellow = motor +

Heating (E93)
purple/green = filament + (with the correct current for a set temperature)
brown = filament -
grey = wire to variable resistor

Heating (E9x)
red/white OR red/brown = filament +
blue/purple = unknown (suspect communication line to HVAC system) = labelled "SHBF_PWM"
green/red = unknown - some kind of low voltage + from fuse 10 (5A) = labelled "15<10"
brown = filament -

Backrest Switch (activates if the seat is folded down)
grey/black = +
grey/white = -

Comfort Buttons (on top of the seat for double speed) - The BMW wiring diagram is WRONG! I learned this the hard way and tested the switch with a multimeter to find these are the true labels:
red/blue = ground
blue/black = backward
white/black = forward

Miscellaneous
orange/green = CAN-high
green = CAN-low
red/black = lumbar +
yellow/white? = temperature (from sensor)

A few notes:
-Yes, it is not quite correct to label these motors as positive or negative since they move in both directions. However, BMW label them this way so I will too.
-*There are a few wires that I am not 100% certain about, they are in italics. You might notice that the backrest angle E46 wire colours are flipped in relation to their E93 counterparts. It seems totally bizarre to me that BMW would flip the wires over, but everything I have seen on the wiring diagrams suggests this is true, and I have successfully wired it in... WEIRD.
-What about the switches!? Unfortunately the switch panels are not transferable between the two seat computers. They use different amperages on each wire and they communicate to the computer in a different way. If you like I can provide more information, just leave a comment. For that matter if anyone wants to see any wiring diagrams go ahead and message me or comment below.

Hope this was helpful to somebody!

[E39 Newbie]

Nice. This may come in handy one day. I didn't see anything in italics. Are the connectors the same between the two seat models? I'd guess not, but one never knows. Do the convertibles have the pyrotechnic charge in the seatbelts? Is that part of the seat wiring?

Thanks for the effort!

[dworthy]

The only other thing I see missing would be the heating elements for the seat heaters.

[Headloch]

Nice. This may come in handy one day. I didn't see anything in italics. Are the connectors the same between the two seat models? I'd guess not, but one never knows. Do the convertibles have the pyrotechnic charge in the seatbelts? Is that part of the seat wiring?

Thanks for the effort!

Italics added in edit, sorry about that. No, none of the connectors are the same between the two seats. Convertibles do come with pyrotechnic seatbelt pre-tensioners, on the e46 they are wired onto the main yellow plug (x279) and on the e93 they are on a separate, smaller yellow connector. The e93 has another wire to detect if the seatbelt is buckled, the e46 does not.

The only other thing I see missing would be the heating elements for the seat heaters.

I shall update the post with the heating wiring now

[dworthy]

Humm, I don't know, but these two wire are for the switch in the buckle receiver: .35 Rot - which comes from Fuse 11 and .35 Swartz aka red and black wires. They connect into X275 at position 5,7 and go out to the car as .35 violet/blau and .35 blau/weis.

X275 is the yellow seat connector for the main harness. Oh and it technically doesn't use a switch, but a hall effect sensor to tell if the buckle is connected or not.

[Headloch]

Humm, I don't know, but these two wire are for the switch in the buckle receiver: .35 Rot - which comes from Fuse 11 and .35 Swartz aka red and black wires. They connect into X275 at position 5,7 and go out to the car as .35 violet/blau and .35 blau/weis.

X275 is the yellow seat connector for the main harness. Oh and it technically doesn't use a switch, but a hall effect sensor to tell if the buckle is connected or not.

Nice, I'll have a look. On E46 the X275 is the driver's side main yellow harness, X279 is passenger side. What you are saying sounds familiar but it most only be true for non-convertibles; when I actually had a look at the seat, there were only two wires attached to the buckle - both for the explosive charge. So there is no way for the car to tell if you are buckled in, and the seat-belt light just illuminates for a few seconds on startup to remind you. On the E93 though, there IS a 'switch' on the buckle.

[dworthy]

After looking at the parts cross index, I did see that the convertible uses the same buckle as all the others: RealOEM.com - Part Search

Of course the belt will be different as it would be specific to the convertible itself.

Also as an add, there is a split in 2001 where the part numbers change, not sure if it would be a upgraded restraint system after that or not.

[Headloch]

Curious. You are right, and realoem says the pre-2001 buckles were interchangeable too. Nonetheless I know for a fact that the convertibles do not have belt buckle detection. My theory is that BMW did not wire the belt-buckle detection on convertibles because the seatbelt light serves a different function - it flashes if either of the seats are folded down.

[ConvGeorge]

Just thought I'd throw this at you - an e64 6-series convertible seat will go into an e46 convertible plug and play. I replaced my driver's seat with one from a M6, and it's significantly more comfortable due to the extra padding and better leather.

[E39 Newbie]

Just thought I'd throw this at you - an e64 6-series convertible seat will go into an e46 convertible plug and play. I replaced my driver's seat with one from a M6, and it's significantly more comfortable due to the extra padding and better leather.

Thanks for this! Now if I could only find a pair in Hellbeige...

[JDP530]

I purchased a pair of E64 seats to put in my E31 since the convertible seats have the integral seatbelt I need for the 850i. But I am still struggling to figure out the wiring. Seats seat a deep cleaning and I may remove the covers and re-work the foam because other seats had been piled on the seats I bought so there are some creases and depressed foam that needs to be rejuvenated.

PXL_20220916_144701377.jpg

[ConvGeorge]

Thanks for this! Now if I could only find a pair in Hellbeige...

I managed to track down a good black M6 vert passenger seat on eBay last month - so now I have matching M6 seats in my 330CiC. Drove there without the passenger seat, put it in right there, plugged it up and everything worked (much to the surprise of the guy working there.) Only issue was the passenger occupancy sensor is either different or bad, I'm just going to code it out.