Further to front and rear ABS solenoid valves (Maintain pressure and Reduce pressure)

The function of the solenoid valves or the return pump is not OK. If a solenoid valve has a mechanical fault, the fault is not  stored in the fault memory.

Hydraulic or electrical lines could be swapped.

If a fault is stored in the fault memory, first eliminate this fault.

Test step "Maintain pressure" not OK: 

• Brake pedal not pressed or not pressed at the right time.
• Electrical or hydraulic lines swapped if the activated wheel locks up (precondition: corresponding inlet valve activated with the "F8" key).
• Inlet valve faulty.

Test step "Reduce pressure" not OK: 

• Brake pedal not actuated.
• If the activated wheel does not  alternately lock up and then rotate freely again but another wheel (precondition: the parking brake is not engaged and the selector lever of Tiptronic vehicles is in position "N"), the hydraulic lines are swapped.
• Outlet valve defective.