lock AUDI A4 1995 B5 / 1.G Brakes Output DTM 03 Workshop Manual

01-152

During the test, the individual test steps are
shown in the second line of the VAG1551
scan tool display. The following
abbreviations are used.
IV = Inlet valve
OV = Outlet valve
LF = Left Front
RF = Right Front
LR = Left Rear
RR = Right Rear
B+ = Battery Positive Voltage (B+) at valve
0V = 0 volts; No voltage at valve
Locked/free = Wheel condition; must be checked
by second technician
Hydr-P = Hydraulic pump
Pa
ge 5 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-154

Output Diagnostic Test Mode (DTM)
-
ABS hydraulic pump -
V64-

Indicated on display:
ABS/EDL hydraulic pump -V64- must start running. This is audible.

When you put your foot on the brake pedal you can feel it vibrating. The
brake pedal vibrates because the hydraulic pump generates pressure
pulses in the brake lines. The pressure pulses generate oscillations.
These are directed to the brake pedal and make it vibrate.
The pressure pulses in the brake lines are not sufficient to lock the
wheels.
The hydraulic circuit diagram shows a systematic representation of
an ABS/EDL system. This will give a better understanding of the
various test steps in the output Diagnostic Test Mode (DTM).
shaded components are in action.Thin solid lines represent hydraulic lines or hoses that are not under
pressure. Thick broken lines represent hydraulic lines or hoses working as
suction lines. Thick solid lines represent hydraulic lines or hoses that are under
pressure.
-
Press button.
Pa
ge 7 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-155

Output Diagnostic Test Mode (DTM)
-
Operate brake

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Ifl: 0V
Ofl: 0V
fl wheel locked

Indicated on display:

When you press the brake pedal, brake fluid pressure will be built up in all
four calipers. All four wheels lock.
Requirement for this: mechanical/hydraulic components of the brake
system must be fully functional. This means that the master brake cylinder
is able to build up pressure in all wheel cylinders and the hydraulic
connections and lines are all sealed properly. If the wheels do not lock,
visually inspect brake fluid reservoir, master brake cylinder, hydraulic unit,
and calipers.
Concentrate on the left-front wheel first. The function of the control
elements for this wheel is tested first.
Note:
This test step in the output diagnostic test mode corresponds to the
"pressure build-up" phase during ABS-controlled braking.
Pa
ge 8 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-156

-
Press button.Output Diagnostic Test Mode (DTM)
-
Ifl: B+
Ofl: 0V
fl wheel locked

Indicated on display:
Keep pressing brake pedal.

Inlet valve is activated. It interrupts the brake line. However, fluid pressure
is still maintained in the wheel cylinder. The left-front wheel remains
locked.
Note:
This test step in the output diagnostic test mode corresponds to the
"maintain pressure" phase during ABS-controlled braking.
-
Press button.
Pa
ge 9 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-159

Output Diagnostic Test Mode (DTM)
-
Ifl: 0V
Ofl: 0V
fl wheel locked

Indicated on display:

Keep pressing brake pedal. Inlet valve is no longer being activated. It is
no longer interrupting the brake line. The brake pedal will give perceptibly
under your foot. Fluid pressure is built again in the left-front caliper. The
wheel will be locked.
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Release brake

Indicated on display:
-
Press button.
Pa
ge 12 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-160

Continue output Diagnostic Test Mode (DTM)
in order to check the front right, rear left, and
rear right wheels in sequence. The test steps
indicate the procedure for the front left wheel.
They will therefore not be repeated in detail. Output Diagnostic Test Mode (DTM)
-
Operate brake

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Ifr: 0V
Ofr: 0V
fr wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Ifr: B+
Ofr: 0V
fr wheel locked

Indicated on display:
ABS/EDL hydraulic pump -V64- must start running.
The brake pedal must not give. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Ifr: B+
Ofr: B+
fr wheel free

Indicated on display:
ABS/EDL hydraulic pump -V64- will stop running. -
Press button.
Pa
ge 13 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-161

Output Diagnostic Test Mode (DTM)
-
Ifr: B+
Ofr: 0V
fr wheel free

Indicated on display:
Brake pedal must give noticeably. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Ifr: 0V
Ofr: 0V
fr wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Release brake

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Operate brake

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Irl 0V
Orl: 0V
rl wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Irl B+
Orl: 0V
rl wheel locked

Indicated on display:
ABS/EDL hydraulic pump -V64- must start running.
The brake pedal must not give. -
Press button.
Pa
ge 14 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-162

Output Diagnostic Test Mode (DTM)
-
Irl B+
Orl: B+
rl wheel free

Indicated on display:
ABS hydraulic pump -V64- will stop running. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Irl B+
Orl: 0V
rl wheel free

Indicated on display:
Brake pedal must give noticeably. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Irl 0V
Orl: 0V
rl wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Release brake

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Operate brake

Indicated on display:
-
Press button.
Pa
ge 15 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-163

Output Diagnostic Test Mode (DTM)
-
Irr: 0V
Orr: 0V
rr wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Irr: B+
Orr: 0V
rr wheel locked

Indicated on display:
ABS/EDL hydraulic pump -V64- must start running.
The brake pedal must not give. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Irr: B+
Orr: B+
rr wheel free

Indicated on display:
ABS/EDL hydraulic pump -V64- will stop running. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Irr: B+
Orr: 0V
rr wheel free

Indicated on display:
Brake pedal must give noticeably. -
Press button.
Output Diagnostic Test Mode (DTM)
-
Irr: 0V
Orr: 0V
rr wheel locked

Indicated on display:
-
Press button.
Output Diagnostic Test Mode (DTM)
-
Release brake

Indicated on display:
Pa
ge 16 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13

01-164

Output Diagnostic Test Mode (DTM)
-
EDL valves/ Hydr-P : B+ Wheel fl/fr lock

Indicated on display: Only significant for troubleshooting on
vehicles with EDL, starting with production deadline of calendar
week 21/1997. For these vehicles, the test step was modified in
parallel to implementation of EBD emergency mode. Prior to
production deadline of calendar week 21/1997, the hydraulic pump is
not activated. This test step does not apply to vehicles without EDL.
The vehicle version, as relates to EBD, can be recognized by checking
the note column under "Check control module version"; page 01
-128
.

The EDL change-over valve (left) and the EDL inlet valve are activated.
ABS return flow pump -V39- runs for one second. It draws brake fluid from
the brake fluid expansion tank via the EDL inlet valve. The hydraulic pump
builds brake fluid pressure in the EDL regulated wheel cylinders. These
wheels will then be locked.
If not, this indicates a mechanical malfunction in one of the valves,
providing there is no electrical malfunction in the system. Replace
hydraulic control unit.
This test step cannot be performed on vehicles that are not equipped with
EDL. These vehicles lack the EDL valves and the pressure relief valve.
Pa
ge 18 of 66 Out
put Dia
gnostic Test Mode
(DTM
) (function 03
)
11/20/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.SU02.01.13