NoQuarter

You can get the seat backs off while the seats are in the car. From there you can see both motors and part of the gearing assembly that moves the bolsters.

AI001

NoQuarter, from this retrofit of yours do you remember if there was a difference in wiring between driver and passenger seat for the active backrest. Looking at my seat wiring it seems like these new seats I have installed have different wiring in the passenger side. Active backrest on the driver side takes power from PIN 25/24 as in this diagram and passenger side is like this diagram where they are powered by PIN 14/13.

At the moment connecting PT CAN lines to my passenger seat makes PT CAN line go dead. Everything on PT CAN line stalls including driver side blosters. This is just by connecting the wires to the passenger side and powering up the car, whole car behaves weirdly, like wipers going off and all sorts of error reported on the dash. Take the newly made connection to the passenger side out and all goes back to normal. This makes me believe active backrest module is fried on the passenger side. I want to swap passenger side control module to the driver side, do you know how to take out the control module (that black plastic box) for active backrest module A854 as given here.

NoQuarter

The symptoms you describe with the wipers going off and such are similar to what happens if the wrong communications signal is patched into the canbus - so either you have kcan into pt-can for example OR the module is bad like you said. To remove the module you will need to take the seat out again to get it out from the bottom. it is held in place by a couple snap tabs that hold onto one of the cross-bars and a single screw. The catch is I don't know how to get to the screw short of removing the seat cusion. I installed my modules and couldn't get to the screw so used zip ties instead because I didn't want to remove the seat leather cover and cusion. But there may be another way I just couldn't figure it out not having seen one properly installed.

From the persepective of the seat harness, the wiring is identical with the exception of the extra ground to indicate passenger/driver side. Where power comes from the car would be different which is what you describe with pins 25/24 from the car and 14/13 from the car but they go to the exact same place on the seat module. Instead of trying to swap modules to test, can you run the drivers side wires over to the passenger module to see what happens?

Also, remember that canbus networks are a low-voltage, signal difference type communication protocol so the signal on the wire can be sensitive to interference. The wires must be twisted like a computer network twisted pair cable. If you made a fairly long run to get pt_can from under the dash to the seat perhaps you are getting a bad signal?

spediegunz

No quarter it seems like you know a lot about this stuff and I figure instead of starting a new thread id just jack yours. Reading your thread has made me want to change out my seats I have a US 530i 2004 just memory seats with lumbar adjustment. Suppose I could some how score a nice deal on some used comfort/active/sport/heated seats what would I need to do to get them retrofitted with all options working on my car I only have the dsc button so I suppose i gotta get a new button panel that supports all those features, but would the chairs be pnp if i transplanted them from a pre lci m5? Where should I start to make this dream a reality.

NoQuarter

Nothing about it will be pnp but it can certainly be done. My first recommendation is for you to begin to understand how to read diagrams like the ones mentioned by Al001 in post # xxx above. This is what is required in order to learn where canbus signals like pt-can or k-can must go, power and ground of course, and so on. Find the diagrams for your existing model year and seats, print them out and take your existing seats out and track down the wires and satisfy yourself you understand how your seats work and how they connect to the car. This is exactly what I did for my seat project - took one out and learned how it worked, put it back then worked on my parts order and harness making.

Finally, you will need to be able to code your car to work with the new modules so you will want NCS Expert software, OBD cable and reading up on the various coding threads in this forum or at east track down a forum member that can code it for you.

spediegunz

thanks for the reply I was hoping it would be pnp im going to take a look at the wiring diagrams suggested . Its all in the if stage now, but i have seen an m5 at a local junk yard should I feel like this is something I can handle maybe I'll try it out but i must admit the wiring gets me nervous. as far as the coding goes I can probably handle that part as ive coded a few options on my car already with ncs

AI001

Update:

Good news, all functional now. No problem with the module. You were spot-on mate, it was my cabling. For some reason connecting PT_CAN line on the passenger side was simply making whole PT_CAN line go wrong, even with no module connected. When I connected the driver side module to the passenger side it was no different. Just to test it further when I connected my custom harness directly the module pins PT_CAN ws fine, this gave me hope. I still don't know why the hell a few extra centimeters of stock car harness will cause such PT_CAN to go dead.

Once PT_CAN line was sorted I thought I will check if the module responds to the tool32. I had driver side module disconnected. To my surprise passenger side module was only responding as driver side module and it took FLBV coding using NCS. Driver side bloster switch was controlling passenger side blosters. This made me happy in a way that atleast module isn't dead.

Part number of both the module were the same. Was wondering what distinguishes between them, found it was an extra ground (just like seat module) connected to pin 7 X11550, connected that as soon as realized and then passenger side BLBV module took coding and all was working as expected.

Long journey though but made there in the end. That bloody wiring investigation took a good portion of 1.5 days of hard labour, constantly marred by worry. btw. just to let you know I could not take the module off from driver seat, when I said I took the module off I meant I only took out the module circuit out of box which was much easier and (possibly only) way to take it out. Module is designed not to be taken out, all due to a screw between seat underside and module topside making it highly inaccessible, if not impossible. You can do it if you have right tools but I didn't. Definetely some bas**rd designed it, a stupid of high grade.

Cheers mate. All done and dusted now. Once wiring is investigated and fixed I will wrap all up and call it a day.

NoQuarter

Great persistence on your part - well done! Please come back after a while and let us know what you think of the Active Backrest function. I thought it would be a cool project and the backrest somewhat of a gimmick but I really like it. I'll look you up again to make some progress on the Sport Automatic Trans upgrade.

AI001

Yes will report back soon. Still I need to figure out why is driver side so noisy.

Btw. do you lubricate/apply grease to the moving part of the seat? Perhaps driver side backrest motors lacking lubrication.

NoQuarter

You can get to the gear part with the back seat cover removed. There is a clear snap on cover over the motor connection to the gear drive. Maybe something there will be evident.