Been having an issue with my transmission for a few months now. It doesn't happen all the time but it has been becoming more frequent. I'll be driving, usually on the highway and there's a hard shift and then the car gets stuck in 3rd gear and the transmission malfunction warning comes up on iDrive. When I park the car and wait a few minutes then turn it back on it shifts normally again.

Then a few weeks ago I put the car in park, turned it off, took my foot of the brake and it rolled backwards like it wasn't in park until I put my foot back on the brake and put the parking brake on. I don't know if this has happened since because I've been using the parking brake ever since just to be safe.

I took it to the dealer after the first time and they recommended that the gear shifter and position sensor be replaced. They weren't sure that's what it was and I didn't want to start throwing money at it so I said I would wait. After the second issue I took it back and they said they were almost certain that this was the issue. The recommended action was to replace the gear selector lever with sensor and program.

I know it's pretty easy to replace the entire gear shift assembly since it's electronic so I was planning on doing it myself. So my question is, is the sensor in the assembly? I can't find any info on this. And does it have to be programmed after the new one is installed? I'm thinking of getting a used gear shift assembly.