After repairing leaking of the two rear brake lines and losing a lot of fluid and introducing air into the system, I'm no longer able to bleed the same two lines. virtually no fluid comes out the lines. The fronts are ok. I bleeded the master cylinder. On checking the rear lines on the DSC noticed there was no fluid so I drove on ice and activated the DSC, check the lines on DSC there was fluid there. Tried the rear lines for bleeding, still nothing. Any suggestions will be appreciated. Thanks
As Ben suggested, the control valves inside ABS module have to be activated in order to flush or bleed the brake lines between the master cylinder and brake calipers.
Driving on ice will only activate the solenoids momentarily, so it isn't a particularly efficient (or safe) way to bleed the brake lines.
The usual way to activate the solenoid involves dealership software (GT1 or DIS). There are rumours that INPA can also activate the solenoid but I was never able to figure it out.