I run a small delivery side business on top of my normal job, and my 2015 BMW M3 is the car I use for it, so every day it sits in a garage costs me money. That is why this problem is stressing me out so much. About ten days ago the dashboard showed a gearbox fault and the car dropped into a slow mode where it would only use a couple of gears. I switched it off, waited a few minutes, and it went back to normal, so I carried on like nothing happened. Then it happened again twice this week, once on a main road with trucks behind me, which was not fun. A friend who knows a bit about cars said it could be a sensor, low oil, or a problem inside the clutch unit, and that scanning the car is the first thing to do. Another friend said just clear the error with a cheap reader and keep driving, but that sounds risky to me. I read about it one evening and opened a page about BMW cars on a Sharjah website to understand how the fault warning works and why the car limits itself on purpose. It explained that this mode is a protection, and that some causes are small while others can grow if ignored. That convinced me not to wait. A colleague who loves fast cars told me to look for a Fast BMW gearbox specialist serving Industrial Area 10 , because he said a few workshops there can finish smaller gearbox jobs in a day or two if they have the parts. I know fast should not mean careless, so I would like to hear real stories before choosing. How long does a proper diagnosis take on an M3, and can the car be used while waiting for parts? Is it normal for a garage to ask for a deposit before the scan? What fault codes usually come with this kind of limp mode, and should I ask for them in writing? Also, if the repair is small, like a sensor or an oil service, how much should I expect to pay? If this happened to your M3 or another BMW, please tell me how it ended and how many days you were without the car. Thanks a lot.