Why is my Closed Loop Fuelling not working

Fuel Closed Loop control will not enable unless the following conditions are valid:

• Engine State must be Run 
• Engine Post Start Fuel Compensation must be zero 
• Engine Overrun must be inactive 
• Exhaust Lambda must be valid 
• No Fuel or Ignition cuts are active (see Cut Count)
   

If your Lambda sensor is working correctly and reporting a Lambda value, but the Closed Loop Enable is remaining as Disabled, and the Fuel Closed Loop Diagnostic is reporting Sensor Unavailable, then the usual cause of this occurring is that the Engine Crank Fuel Volume Compensation table does not have 0.0 as the last value in the final column.  

Having a non-zero value in the final column of this table will prevent the Closed loop from operating.