One more thing to add:
The ACC doesn't just rely on the forward-facing radar, but it also relies on numerous speed sensors on your bike to make everything work smoothly. One quick sensor to check is your front ABS speed sensor. It's the sensor that sits between the disc with a bunch of slots in it; That's your speed sensor disc. If that gets just dirty enough, it might be enough to trigger the ACC warning but not the ABS? I don't know for sure since BMW doesn't offer service manuals, but it'd be something I'd check for.
What other issues have you had with your Beemer? This might be related.
Mike
The ACC doesn't just rely on the forward-facing radar, but it also relies on numerous speed sensors on your bike to make everything work smoothly. One quick sensor to check is your front ABS speed sensor. It's the sensor that sits between the disc with a bunch of slots in it; That's your speed sensor disc. If that gets just dirty enough, it might be enough to trigger the ACC warning but not the ABS? I don't know for sure since BMW doesn't offer service manuals, but it'd be something I'd check for.
What other issues have you had with your Beemer? This might be related.
Mike