Meaning: Driver release driver: VZA controls driver but driver checkback signal missing.
Effect: Driving switched off (drive, Mikropils, brake)
Possible cause: driver on SK-VZA defective.
Measure: status analysis MZ-100, visually inspect SK-VZA, replace if necessaary. Before starting check the protection circuit of the drive contactors.
VZA: is the driver compartment processing unit
Also check the microfuses. The cards in the VZA and VZK are interchageable, so you might be able to identify a faulty card by swapping. There are some measures to be taken before swapping. If you need these email me.