Audi Workshop Service and Repair Manuals

Final control diagnosis The final control diagnosis can be used to check the ABS hydraulic pump -V64- and the correct functioning of the hydraulic circuits (allocation of brake pipes to wheel brakes and function of valves). This function will also detect interchanged connections and leaks.   Note t  The vehicle must be raised until all wheels are free to turn. A 2nd mechanic is required in order to turn the wheels. t  To avoid overloading the control elements they are only activated for a period of 60 or 90 seconds. The final control test will be terminated if the → key is not pressed within this period. t  The ABS warning lamp -K47- and the red “brake warning” symbol flash during the final control diagnosis. t  After depressing the brake pedal several times the vacuum in the brake servo will be exhausted. Therefore more pressure must be applied to the brake pedal in order to attain the same fluid pressure in the brake system as that attained with vacuum. t  When vacuum in brake servo is exhausted it can happen that the wheels do not lock: start engine and build up vacuum in brake servo. Explanation of abbreviations indicated on display

IFL	=	Inlet valve (front left)
IFR	=	Inlet valve (front right)
IRL	=	Inlet valve (rear left)
IRR	=	Inlet valve (rear right)
OFL	=	Outlet valve (front left)
OFR	=	Outlet valve (front right)
ORL	=	Outlet valve (rear left)
ORR	=	Outlet valve (rear right)
VBAT	=	Battery voltage; voltage is applied to valve
0V	=	0 Volt; No voltage at valve
Hydr-P	=	ABS hydraulic pump -V64-

Components of the ABS/EDL system The hydraulic circuit is a schematic diagram of the ABS/EDL system. The diagram shows only one brake circuit. 1 -  Low pressure accumulator 2 -  ABS hydraulic pump -V64- 3 -  EDL inlet valve (hydraulic) 4 -  Noise damping chamber 5 -  EDL change-over/separating valve (electrical) with integrated pressure limiting valve 6 -  Front inlet valve 7 -  Front outlet valve 8 -  Front wheel 9 -  Rear inlet valve 10 -  Rear outlet valve 11 -  Rear wheel Test condition l  The wheels are locked individually during final control diagnosis. For this test the mechanical and hydraulic components of the brake system must be working properly. This means that the master cylinder is able to build up pressure in all four wheel brake cylinders and there are no leaks in the hydraulic pipes, hoses and connections.   Note If one of the wheels does not lock, perform a visual inspection of the brake fluid reservoir, the master cylinder, the hydraulic unit and the wheel cylinders. Procedure –  Connect vehicle diagnostic, testing and information system -VAS 5051 A- → Chapter and select vehicle system “03 - Brake electronics”. When doing this the ignition must be switched on.

Indicated on -VAS 5051 A-: –  Release handbrake. –  Raise vehicle on lifting platform. –  From list -1- select function “03 - Final control diagnosis”.

Indicated on -VAS 5051 A-: A -  Final control test waiting, move on to next control element 1 -  ABS hydraulic pump V64 –  Touch → key. Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 1 -  ABS hydraulic pump V64

l  The ABS hydraulic pump -V64-- item 2- should start up audibly.   Note t  When you put your foot on the brake pedal you can feel it vibrating. This is because the hydraulic pump -V64- is producing pressure pulses in the brake pipes. The pressure pulses induce the vibrations that can be felt at the brake pedal. t  The pressure pulses in the brake pipes are not sufficient to lock the wheels. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 2 -  Operate brakes –  Depress brake pedal and and touch → within 10 seconds.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 3 -  IFL: 0V  OFL: 0V   Wheel FL locked

l  Brake pedal should not give under foot pressure. l  When you press the brake pedal, brake fluid pressure will be built up in all four wheel brake cylinders. l  The hydraulic EDL valve -3- closes, the front wheels -8- and rear wheels -11- are locked.   Note This test step in the final control diagnosis corresponds to the“pressure build-up” phase during ABS-controlled braking. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 4 -  IFL: VBAT  OFL: 0V   Wheel FL locked

–  Keep pressing the brake pedal. l  The hydraulic EDL valve -3- remains closed. l  The front inlet valve -6- is activated, which interrupts the supply to the wheel brake cylinder; however, the fluid pressure is still maintained in the wheel cylinder. l  The front left wheel -8- remains locked.   Note This test step in the final control diagnosis corresponds to the“maintain pressure” phase during ABS-controlled braking. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 5 -  IFL: VBAT  OFL: VBAT   Wheel FL free to turn

–  Keep pressing the brake pedal. l  The inlet valve -6- and the outlet valve -7- for the front left wheel -8- are activated. l  The ABS hydraulic pump -V64--item 2- starts running and reduces the brake fluid pressure in the wheel brake cylinder via the open outlet valve. l  The brake pedal must not give, and should press back harder against your foot. l  The front left wheel -8- is free to turn.   Note t  This test step in the final control diagnosis corresponds to the“pressure reduction” phase during ABS-controlled braking. t  If you cannot turn the front left wheel, check whether the brake line for the front left wheel is correctly connected. t  If this is the case, this indicates that there is a mechanical fault in one of the valves, providing that there is no electrical fault in the system. Renew the hydraulic control unit → Brake system; Rep. Gr.45. t  If the brake pedal gives under your foot, this means that the inlet valve or the non-return valve connected in parallel with the inlet valve is leaking. Renew the hydraulic control unit → Brake system; Rep. Gr.45. –  Touch → key within the next 10 seconds.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 6 -  IFL: VBAT  OFL: 0V   Wheel FL free

–  Keep pressing the brake pedal. l  The hydraulic EDL valve -3- remains closed. l  The ABS hydraulic pump -V64-- item 2- should stop running. l  Only the inlet valve -6- is now activated, and this interrupts the supply to the wheel brake cylinder. l  The front left wheel -8- is free to turn.   Note If the wheel is not free to turn, this means that the inlet valve or the non-return valve connected in parallel with the inlet valve is leaking. Renew the hydraulic control unit → Brake system; Rep. Gr.45. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 7 -  IFL: 0V  OFL: 0V   Wheel FL locked

–  Keep pressing the brake pedal. l  The inlet valve -6- is no longer activated and does not interrupt the supply to the wheel brake cylinder. l  Brake pedal will give perceptibly under your foot. l  Brake fluid pressure is built up again in the front left wheel cylinder -8- - the wheel is locked. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 8 -  Release brakes –  Release brake pedal. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 9 -  Operate brakes   Note t  Continue the final control diagnosis to check the front right, rear left and rear right wheels in turn. t  The test steps are the same as for the front left wheel, so they are not described in detail. After testing on rear right wheel is completed: –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis running, moving on permitted 30 -  EDL valves/Hyd-P: VBAT FL/FR wheel locked

l  The EDL change-over valve -5- and the EDL inlet valve -3- are activated. l  The ABS hydraulic pump -V64-- item 2- should start running for one second. The pump draws brake fluid out of fluid reservoir via EDL inlet valve. l  The hydraulic pump builds up brake fluid pressure in the EDL controlled wheel brake cylinders. The front left and front right wheels -8- are locked.   Note If the front wheels are not locked, this indicates that there is a mechanical fault in one of the valves, providing that there is no electrical fault in the system. Renew the hydraulic control unit → Brake system; Rep. Gr.45. –  Touch → key.

Indicated on -VAS 5051 A-: A -  Final control diagnosis competed –  Terminate function “03 - Final control diagnosis” by pressing the ← key. l  Final control diagnosis is completed. The ABS warning lamp -K47- and the red “brake warning” symbol should go out.   Note t  There is a fault in the system if the ABS warning lamp -K47- does not go out. t  Adhere exactly to the test sequence: First interrogate fault memory, then erase.