To access a whole slew of data and the instrument cluster test on an e46:
1. with the ignition off, hold the left instrument button
2. turn the key to position 1 (radio)
3. If you let go of the button and press again you will cycle through the following 20 tests.
4. If you want to acess the submenus, release the button while a test menu number is being diplayed, within a second, you will see Test number.0. You can then click again to cycle through the submenus. To get back to the main menu, press and hold the left key until you see the test number without the ".0".
5. Note, you can only access tests 1 and 2 without unlocking-- to unlock the other tests, go to test 19 and wait for the display to say "l-off", then click again. Now you can cycle through to the other tests