BMW M3 Speedometer Glitch: Error Code Mystery Solved

Hi! I've got some experience working on BMWs, having owned a 1999 BMW M5 and currently drive a 2003 BMW 325i. Had a similar speedometer issue on my M5 last month. The error message was quite annoying, and I was concerned at first. Took it to my regular workshop for an OBD2 scan since they do free diagnostics for regular customers. Turned out it was just needing a system readout and reset, nothing serious. But before I can suggest more specifics about your case, could you share: What's the exact error message you're seeing? Has the speedometer behavior changed recently? Any other warning lights on? Have you had any recent work done on the car? This info would help me understand if your issue matches what I experienced.

Thanks for the detailed response! Yeah, should've provided more info. The error message says "Speed Input Signal Fault" and it started showing up right after my last service about 800 KM ago. The speedo works intermittently now, sometimes perfect, sometimes totally dead. No other warning lights though. My M3 has 179560 KM on the clock, and I've been pretty good with maintenance. Really hoping it's just a reset thing like yours was and not the speed sensor going bad. The intermittent nature is what's got me scratching my head.

Oh that definitely rings a bell! Had the exact same "Speed Input Signal Fault" message on my M5 actually, what a coincidence. The intermittent behavior you're describing is exactly what I dealt with too. Initially thought my system readiness reset fixed it, but the problem came back after about 1000 KM. Turned out the speed sensor was starting to fail, but wasn't completely dead yet, that's why it was working on and off. Since you mentioned it started after your service, they might have disturbed something while working on the car. In my case, the sensor was showing signs of corrosion when they pulled it out. Cost me around 300 for the part plus labor, but it's been perfect since the replacement. Much better than having an unreliable speedometer! If you're mechanically inclined, you could check the sensor connections first, sometimes it's just loose wiring. But given the age of our cars and the symptoms you're describing, I'd bet you're looking at a sensor replacement too. Let me know what you find out. Always interesting to compare notes with other BMW owners, especially with such similar issues!

Thanks so much for sharing your experience! That's super helpful, especially since you dealt with the exact same error message. The fact that yours was also intermittent before the sensor completely failed makes me feel better about my diagnosis. I'm decent with basic maintenance, but I think I'll leave this one to the pros, don't want to risk messing anything up further. I'll schedule an appointment tomorrow and have them check those sensor connections first, just in case. But you're probably right about needing a replacement given the car's age. 300 for parts and labor doesn't sound too bad at all, I was worried it might be something way more expensive. Really appreciate you taking the time to explain your experience with this issue. I'll definitely update you once I get it sorted!