BMW Won't Start in Park, Transmission Lock Mystery

I had a similar issue with my 2008 BMW 5 diesel last year. The symptoms you're describing match what I experienced, rough shifting, starting problems, and the dreaded check engine light. After taking it to the garage, they diagnosed an "Affected Control Unit" problem in the transmission system. My EGS (transmission control unit) was failing. It was a serious issue that needed immediate attention since it affects the entire transmission operation. The repair involved replacing the control unit and reprogramming the new one to sync with the car's systems. Had to leave the car at the shop for 3 days, but it's been shifting smoothly ever since. The parking lock mechanism was actually fine in my case, it was all down to the electronic control unit. Based on what you're describing, I'd recommend getting the transmission control unit checked first before looking at mechanical issues. It's not something you want to leave unattended as it can lead to complete transmission failure.

Thanks for sharing your experience! I went through something similar with my EGS unit. Really glad it worked out for you with the control unit replacement. Just curious, do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since then, or have you noticed any other transmission quirks pop up? Always good to know what to watch out for with these cars.

Hey there! Happy to give you an update. After getting it fixed, I paid exactly 1000 € for the control unit replacement and programming, pretty much what I expected after the diagnosis. And I've got great news, the transmission has been working like a charm since the repair! The parking position issue that was giving me headaches is completely sorted now. It's been such a relief not having to deal with those annoying starting problems or rough shifts anymore. The car feels like new when switching gears, and that pesky check engine light hasn't shown its face since. I can finally use the parking position without any worries, it engages perfectly every time. I know we were all a bit worried about potential transmission issues popping up later, but I can honestly say I haven't had a single problem since the fix. The mechanic really knew what they were doing with the control unit replacement. Looking back, it was definitely worth every penny just for the peace of mind. My advice? If you're experiencing similar symptoms, don't wait around hoping it'll fix itself. Better to address it before it potentially turns into something bigger!

Thanks a lot for the detailed follow-up! I actually just got back from the mechanic yesterday, and you won't believe it, I had almost the exact same fix done. My story's a bit different though. I found this experienced BMW specialist who diagnosed it right away. The transmission control unit was shot, just like yours was. The whole thing set me back about 1200 €, a bit more than yours because they had to fix some wiring issues too. But honestly, after driving it today, it feels like a completely different car! The transmission shifts are butter smooth now, and that stubborn check engine light finally turned off. Funny thing is, I was so worried it would be a complete transmission replacement, which would've been a nightmare cost-wise. Really relieved it turned out to be just the control unit. The car starts perfectly now, regardless of gear position, and the parking lock clicks in place like it should. Thanks again for sharing your experience, it really helped me understand what I was dealing with. It's great to know I can count on this fix to last, seeing how well yours has held up!