Some of us would like to be able to get a heated steering wheel work on older cars.
Sadly, the more I look into this the less likely it seems that it will be possible. Originally I was convinced that all of the necessary hardware was in the steering wheel itself, but after managing to get my local service centre to try and activate the 2021 wheel fitted to my 2020 M3P (as if it was a 2021 car that turned up with the option not enabled by mistake), they spent 3.5 hours and didn't get anywhere. They told me that they were able to modify the gateway configuration to tell the car that it had a heated steering wheel present, but the option to switch it on never appeared on the car screen.
Their conclusion was that there was other hardware in the car that was different. They speculated that it could be a revised left body controller, or harness, or both. After going home dejected I did some research and found out that there are several left body controller part numbers, presumably for different model years.
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The long and short of it is that the current body controller fitted to 2021 cars is electrically different to the ones that came before it (including the one I have fitted in my car). The connectors from the harness that attach to it are physically different, so at the very least if this part needs to be changed then the harness does too, together with whatever connects at the other ends of it, which presumably has different connectors as well. A pretty significant job.
I have been following someone who managed to brute force the gateway configuration to get the heated wheel control to appear on the screen, but it still doesn't work. He has speculated that there is some sanity check of the left body controller that stops the necessary control messages from getting through.
My local service centre proactively messaged me over the holidays to tell me that they are still looking into this and will be in contact shortly, but I'm not holding out much hope of them being able to progress it any further.