I am in the process of upgrading my stereo system in 2001 X5 with DSP/NAV. I followed Ken's instruction to disable the DSP function:

1. Unplug HU (2 plugs behind NAV Screen)
2. Unplug radio tuner (this one is behind the battery, under the loading floor, I disconnect all the plugs I can find in there, even the FM antena )
3. Unplug DSP amp (3 plugs: a big black plug with the power, a smaller one with all the speaker lines out, and a small black one with the pre-amp signal from the tunner).
4. Wait a few minutes then plug the HU and radio tuner back in. Turn on ignition and the DSP OPTION IS STILL THERE.

I then tried TJJ's way by disconnecting the battery before step 1 and connect battery before step 4 and the DSP option did not become greyed out as it should be. Am I doing something wrong here or this method only work with 2002+ X5?