Possible causes, elimination, notes

The complete hydraulic unit must be replaced if the intake valve is damaged.

In the intake valve test with the Porsche System Tester 2, select Intake valve in the Drive links menu.

Perform the test according to the Tester instructions. If the functions specified in the Tester display: Rear axle locked up / Rear axle still locked / Release (rear axle free) are not achieved, the following faults are possible:

Test sequence not observed.

• Inadequate bleeding of ABD secondary circuit, see MENU: BLEED (ABS/TC 5.3)  .
• Function of the intake valve not OK.
• Return pump operation not OK.

  Check pump operation. To do this, select return pump in the Drive links menu (pump must then run).

• Intake or switch-over valve leaks.