To avoid injury and/or damage to the electronic ignition system, the following requirements must be observed when working on the electronic ignition system:
Wash the engine only with the ignition off.
When performing arc and spot welding, disconnect the battery completely.
Do not disconnect the battery, generator or starter while the engine is running.
When checking compression, be sure to remove the main relay "1" of the DME system to prevent the occurrence of ignition voltage pulses. (2 - DME system fuses). Compression testing is described here.
Disconnect the ignition system wires only when the ignition is off.
Connecting and disconnecting measuring instrument wires (crankshaft speed meter, ignition tester) should be undertaken only with the ignition off. Ignition system output stage (high voltage winding, ignition voltage wires) must be loaded with a resistance of at least 4kΩ;. The spark plug tips must be connected.
Never start the engine with the ignition coil wire (terminal 4) removed.
It is forbidden to connect a capacitor for interference protection and a control lamp to terminal 1 (-) of the ignition coil. It is forbidden to connect terminal 1 of the ignition coil to ground or to the "plus" (+) of the storage battery. Therefore, when installing an additional alarm system, it is forbidden to use the terminal 1 wire to block the engine start. When heated to more than +80°C (for example, varnishing, steaming), do not start the engine immediately after the heating process.
Persons with a pacemaker should not work on electronic ignition systems.
Information taken from this resource «BMWMan.ru»