To change or not to change Glowplug CU

[mcc05]

Hi all,
So if I run a rheingold test on my 2009 E70 X5, with just the ignition on I get the following error codes in the DDE.
004212 DDE: Glow plug, cylinder 1, activation, with existent No
004222 DDE: Glow plug, cylinder 2, activation, with existent No
004232 DDE: Glow plug, cylinder 3, activation, with existent No
004242 DDE: Glow plug, cylinder 4, activation, with existent No
004252 DDE: Glow plug, cylinder 5, activation, with existent No
004262 DDE: Glow plug, cylinder 6, activation, with existent No

However if I start the car and clear the errors they go away, and only come back if I leave it overnight and try again in the morning.

Do I need a new Glowplug CU, and is there any way in rheingold to test the glowplug activation?