BMW 6 Series Auto Trans Failure: Warning Signs & Solutions

Hey there! I had nearly identical issues with my 2013 BMW 5 Series diesel last year. The symptoms matched yours exactly, erratic shifting, warning lights, and limp mode. Thought it was just the transmission fluid too, but my mechanic found it was actually an undervoltage problem causing the transmission control module to malfunction. The real culprit turned out to be a failing voltage regulator and a weak battery. The transmission itself was fine. Had the voltage regulator replaced and installed a new battery, problem solved completely. The transmission went back to shifting smoothly. Just a heads up, while this was my specific issue, transmission problems can be tricky to diagnose. Mine was a serious electrical issue that needed immediate attention to prevent potential damage to other systems. Better get it checked soon by a specialist who knows BMWs.

Thanks for sharing your experience, that's really helpful to hear about the voltage regulator being the culprit. Do you remember roughly how much the repairs set you back? Also curious if you've had any other electrical gremlins pop up since getting it fixed?

Hey again! Just wanted to follow up, got my issue fixed last week and thought you'd like to know how it turned out. Funnily enough, it was indeed the transmission control module acting up due to voltage problems, just like my previous experience. The total bill came to 240 € which included fixing the undervoltage issue. While they were at it, they also checked the automatic transmission oil which turned out to be quite worn, so they took care of that too. Since the repair, my BMW's been running like a dream, smooth shifting, no warning lights, just perfect performance. And nope, haven't seen any other electrical issues pop up. The car feels as good as new now. Really glad I got it sorted before it could cause any bigger problems! Just goes to show how important it is to get these things checked out by someone who knows what they're doing. These BMWs can be tricky, but once you get them sorted, they're fantastic machines.

Thanks everyone for your help and advice! Just wanted to update you on my BMW situation. Finally got it checked out at a specialist shop yesterday. Turns out you were right, it was actually an electrical issue! My case was a bit different though. The mechanic found a faulty wiring harness that was causing intermittent voltage drops to the transmission control unit. The repair was pretty straightforward, they replaced the damaged wiring and did a full system reset. Cost me about 350 in total, including diagnostic time. While they had it open, they checked the transmission fluid too, which surprisingly was still in decent shape. The car's running beautifully now, no more jerky shifts or warning lights. I was really freaking out thinking I'd need a whole new transmission, so I'm beyond relieved it was just a wiring issue. Definitely learned my lesson about getting these things checked out sooner rather than later. Really appreciate everyone's input, helped me feel more confident about getting it sorted!