Hello, I hope the following is of assistance.If the ABS hydraulic unit need purging you may only be able to do this with the correct diagnostic equipment. Regardless of this the brakes need to be bled in the conventional way first.
The system consists of separate circuits for each front and diagonally opposite rear wheel. Each circuit can be bled individually, and each wheel circuit can be bled individually of the other. To bleed is as follows,
Ensure that the vehicle is standing on level ground or on a non‐wheel free hoist.
Remove the reservoir filler cap. Disconnect the low brake fluid level warning light switch multiplug. Remove the filler cap.
Fit a bleed tube to the front left‐hand caliper bleed nipple.
Bleed the circuit.Ensure the bleed tube is a firm fit.Immerse the end of the tube in a bleed jar containing a
small quantity of approved brake fluid.
Position the bleed jar base at least 300 mm above the bleed nipple to maintain fluid pressure and prevent air leaking past the threads of the bleed nipple.
Unscrew the bleed nipple by one turn.
Depress the brake pedal fully (pumping brake fluid and/or air into the bleed jar) and allow the pedal to quickly return to the rest position.
Pause briefly to allow full recuperation of the master cylinder.
Continue pumping until air free fluid is being pumped into
the jar.With the pedal fully depressed tighten the bleed nipple.
Repeat the procedure for the rear right, front right and rear left‐hand brake circuits.
Top up the fluid reservoir to the Max mark.Refit the fluid filler cap and reconnect the low brake fluid warning light switch multiplug.When required, bleed the ABS hydraulic unit by running the bleed option on the diagnostic equipment menu following the instructions given.
I hope this helps but if I can assist further let me know and I'll reply as soon as I can.