Daf 55 LF Fault?

does any one know about this fault? I’m getting a error of “actuator air supply: voltage below minimum threshold or short circuit to ground”
with error code: 1698 PID:-- SPN: 3489 FMI:4 im getting the code from a texa TXT navigator ( not the best diagnostic equipment ive used!!)

this is the only fault on the system and theres no ABS fault coming up on dash or texa the fault only comes up in the diesel system.
Any help would be appreciated

Not a scooby, but if you try to PM a member here called Norb he is a DAF mechanic and should put you right.