The Dark Eldar use these grenades solely for one purpose – to cripple the control systems of an enemy vehicle. This is done by the short-ranged but extremely powerful electro-magnetic pulse that the grenade produces when detonated. The grenade, however, first needs to be clamped in place before activated, which means that each model using a grenade makes only one attack and doesn't count bonus attacks for charging, extra hand weapons, etc. If you hit, roll on the following table to see the effect of the haywire grenade on the target:
1 = No effect 2-5 = Glancing Hit 6 = Penetrating Hit.
Haywire grenades can only be used against Dreadnoughts if the Dreadnought is already immobilised.