BMW 7 Series Speedometer Error & Cruise Control Failure

Hey there! I have some experience working on BMWs and had a similar issue with my 2004 BMW 5 Series last year. Feel your pain with those cruise control problems! Had the exact same symptoms, speedometer acting up and cruise control completely dead. Turned out it was just a faulty wiring connection to the cruise control module. My regular mechanic found some corroded plugs that were causing the communication issues. Total repair cost me 95 Euro, mainly for diagnostic time and fixing those connections. Before I can give more specific advice, could you share if you're getting any specific error codes? Also, have you noticed any other electrical issues? Sometimes these problems can be connected to other systems in these models. Just a heads up, these symptoms can sometimes point to different issues in the 7 Series compared to my old 5 Series, but the wiring is often the culprit in BMWs of this era.

Thanks for chiming in! I've got 141313 KM on my car and had the last service done just three months ago. No other electrical issues that I've noticed, but I think you might be onto something with the wiring suggestion. Mechanic did mention during my last service that some wiring harnesses were showing age. The error code I'm getting is P1635, if that helps narrow things down. Really hoping it's just a connection issue like you had and not something more serious with the module itself!

Ah, that error code P1635 rings a bell! Yeah, I had the same code on my BMW too. Given that your car has similar mileage to what mine had (I was at around 138000 KM when this happened), and considering what you mentioned about the wiring harnesses showing age, I'm even more convinced it's a similar issue to what I experienced. In my case, after the mechanic fixed those corroded connections I mentioned earlier, we actually found a few more worn spots in the wiring harness near the cruise control module. It's pretty common in these BMWs, the insulation just doesn't age well in that area. The fact that you had a service three months ago and they noticed the wiring harness condition makes me think we're definitely looking at the same problem. Quick tip from my experience, when my mechanic fixed it, he actually applied some protective coating to the new connections to prevent future corrosion. Might be worth asking your mechanic about doing the same. It's been over a year now and I haven't had any issues since. Just keep in mind that while the labor cost shouldn't be too bad, prices for BMW parts have gone up quite a bit since I had mine fixed last year. But still way better than replacing the entire module!

Thanks so much for the detailed info, this is exactly what I needed! Really relieved to hear it's likely just a wiring issue rather than a full module replacement. I'll definitely mention the protective coating idea when I take it in. It's actually reassuring to know someone else went through the same thing and got it sorted without breaking the bank. Just scheduled an appointment with my mechanic for next week. I've saved all the details you shared about the connections and corrosion to show him. Was getting worried this would turn into one of those nightmare BMW repair bills, but this sounds much more manageable. Really appreciate you taking the time to explain everything so thoroughly. You've saved me a lot of stress and probably some money too!