abs status

[gwhite]

  working on a 2006 r12rt with Wizzy brakes. the rear brake pedal was hard to push. cleaned up rear caliper and then did complete system flush following manual instructions. everthing is working no fault codes. but in the ABS status section i got these readings.
   
  pressure front wheel control circuit 6.57 bar
  pressure rear wheel control circuit 21.53 bar
  pressure front wheel wheel circuit 20.97
  pressure rear wheel wheel circuit 21.11
what is the wheel control circuit and why would one be reading 6.57?
  the other three readings seem good why would one front wheel reading be so low?

[schuppi]

Error within the control unit. Pressure sensor control circuit out of specification, target = 12-30 bar.
The pump motor does not start with the displayed 6 bar, the brake booster is not built up.
Read out error after test drive, entry will read >17181 Pressure in front wheel circuit to low <