[Brian86]

My e91 with an OE audio system is intermittently detecting a 'false CD' or 'false CD load' which causes the input to switch temporarily to to the CD.

Doesn't seem like a common problem. Looks like it's a lot more likely for CDs to get stuck.

It's really annoying. Particularly now that even with the radio turned off I can still hear the CD player wirrring away trying to load/spin a CD.

I assume there is an optical sensor that is getting triggered (or untriggered) so my first fix will be blowing a can of air into the slot to try and clear any potential debris off the sensor.

Next I think I'll try actually loading a CD. I've had the car for 6 months and haven't actually tried the CD player. Perhaps just leaving a disk in will stop it from getting into a cycle of continuous false-loading.

I'm not opposed to tearing the thing apart. It took about a dozen fixes to my e36 HVAC and radio before they stopped malfunctioning.

[Brian86]

So, bringing this to a close. (in the unlikely event anybody ever searches)

I took the lazy route and loaded an audio CD into the player. Now that it senses the disk it doesn't periodically switch my inputs around.

Not really 'fixed' but 'fixed enough' for me.

[ctuna]

Did you try any kind of cleaning .
1) With forced air of Vacuum as a first attempt .
2) Remove Radio take the cover off and clean and inspect for
dirt and damage.
3)You can get used Radio's pretty cheaply but you have to program
them for the Sound System and options in your car most of the time.

[Hotter]

Remove CD module completely. The module is inside the radio. Its quite easy to remove it from radio just unscrew and unplug it. I don't believe anyone will use CD any more. + you save extra weight = more hp

[Brian86]

I tried blowing it clean with a can of air, and tinkered around with some general internet searches to no avail.

Didn't remove or disassemble it. Perhaps someday but now it's way down life's priority list since I have a 'good enough' fix.