Hello, my fellow gearheads,
At precisely 3:30 pm, I was elbow-deep in a brake job on a 2019 220i Active Tourer F45 sporting a modest 64,000 km. The plan was simple: replace the front and rear brake pads, log the work in BMW’s sacred service history, reset the CBS, and send the customer off with a smile by 4:30 pm. Everything was humming along nicely—until the obligatory test drive.
You see, whenever I do a brake job, I take the car for a spin to “bed in” those new pads. So, naturally, I jumped in, started the engine, shifted into reverse—and nothing. Absolutely nothing. I tried repeatedly: reverse after reverse, gas pedal pressed like a man possessed, and yet the car stubbornly refused to budge. In drive, it prances along like a dream, but reverse? It was as if the gear had taken a long lunch break.
I plugged into the ICOM, ran ISTA, and discovered a handful of EGS (transmission control unit) faults. Now, this is a Getrag DCT-7 transmission, and when it loses its speed signal, it simply throws a tantrum. Except this time, the fault codes were as mysterious as a soufflé that refuses to rise—just a vague “1/2 transmission adaptation” message, with no further explanation.
After a bit of digital poking, I cleared the fault memory. The ECU tree went green, the tests returned empty, and yet, reverse remained dead as a doornail. In desperation, I disconnected the battery’s negative terminal for 20 minutes—a classic cure-all, as any seasoned mechanic will tell you. The owner and I sat, exchanging incredulous glances, as time ticked by.
Upon reconnecting the battery, the car had the audacity to misbehave even more: not only would it refuse reverse, but it also forgot to display any transmission position at all—no P, N, or D. I ran the tests again, saw adaptation errors involving the DME, DSC, EGS, and BDC, cleared the fault memory, and lo and behold, the transmission indicator returned. Finally, reverse and drive behaved as expected. But what on earth had happened?
Then, like a flash of insight (or perhaps the result of too many strong cups of coffee), the culprit emerged. While replacing the brake pads, I’d been cleaning the wheel hubs with my trusty wheel hub grinder. At the rear left wheel, the brake disc spun with such velocity—thanks to my Milwaukee M18—that it apparently upset the delicate balance of BMW’s electronic cosmos. The F45, being a front-wheel-drive marvel, has nothing to hold that disc in place. And so, the rotational madness set off a chain reaction of ghost faults, a veritable electronic tantrum that even the car’s ICOM couldn’t properly explain.
In the end, the car is now as fit as a fiddle—driving away without a hitch. I’ve wasted a good one and a half hours chasing a fault that, frankly, should not even be possible. Kudos to the customer, a remarkably reasonable gentleman, for enduring this automotive farce with a dash of grace.
So, if you ever find your BMW throwing a hissy fit after a routine brake job, remember: sometimes the gremlins are not in the engine, but in the mischief caused by an overzealous wheel hub grinder. Cheers to the madness that makes working on these magnificent machines so utterly unpredictable.
Until next week, keep your brakes fresh and your gremlins at bay!
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