brake fluid AUDI A4 1999 B5 / 1.G Brakes Output DTM 03 Workshop Manual

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
)
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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

01-157

Output Diagnostic Test Mode (DTM)
-
Ifl: B+
Ofl: B+
fl wheel free

Indicated on display:
Keep pressing brake pedal.
The inlet valve and the outlet valve for the left-front wheel are activated.
The hydraulic pump starts running and reduces the fluid pressure in the
caliper via the open outlet valve.

The brake pedal must not give, and should press harder against your
foot.
You should now be able to turn the left-front wheel.
If you cannot turn the wheel, check whether the brake line for the left-front
wheels is connected correctly. If yes, this indicates a mechanical
malfunction in one of the valves, providing there is no electrical
malfunction in the system. Replace hydraulic control unit.
If the pedal gives under your foot, this means that the inlet valve or the
check valve activated in parallel to the inlet valve is leaking. Replace
hydraulic control unit.
Note:
This test step in the output diagnostic test mode corresponds to the
"pressure reduction" phase during ABS-controlled braking.
-
Press button.
Pa
ge 10 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

01-164

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

01-181

Function test: Red brake warning symbol
Test
step VAG
1598
sockets Test of
Test requirements
- Additional work stepsSpecified
value Corrective
action
9 - Function of red "brake
system malfunction"
symbol
Repair Manual, Brake System, Repair
Group 47

Brake fluid level is OK Function of ABS warning light -K47-
already checked in step 8. Multi-pin connector connected to ABS
control module -J104- and retainer catch
engaged. Switch on ignition
Test step 9: Continued on
next page.
Pa
ge 36 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