display AUDI TT 1995 8N / 1.G ATW Engine Additional Signals Workshop Manual

24-156

Engine speed signal, checking


Note:
The engine speed signal is output at terminal 37
of the Engine Control Module (ECM). The signal
is used, among other things, for RPM display in
the instrument cluster.

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
37 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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24-157

Vehicle speed signal, checking


Note:

The vehicle speed signal is generated by the
speedometer Vehicle Speed Sensor (VSS) -
G22- (at transmission) and is processed in the
instrument cluster.
The processed signal enters at terminal 54 of
the ECM and is used for idle stabilization and
tip-in shock reduction during shifting.

Test requirement:
Function and display of speedometer OK.
Troubleshooting:

Repair Manual, Electrical Equipment, Repair
Group 90; Instrument cluster; Speed signal, checking


Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
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24-158

WARNING!

To reduce the risk of accident during road
tests, always observe safety precautions
Page 24
-1 .
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measuring value block
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -0- and -5- to select "display group number 005" and
press -Q- button to confirm input.
Read Measuring Value Block 5
1
2
3
4

Indicated on display
Determining via road test whether vehicle speed is displayed in display
field 3.
- If vehicle speed is not display, lift vehicle -if possible using a vehicle lift-
until front left wheel is free.
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24-161

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measurin
g value block
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -0-, -5- and -0- to select "display group number 050" and
press -Q- button to confirm input.
Read Measuring Value Block 50
1
2
3
4

Indicated on display(1 to 4 display fields) - Switch A/C system off.

Specified value in display field 4: Compr. OFF
- Switch A/C system on using "Auto" button and adjust A/C system to
maximum cooling or heating power. Compressor must run.
Specified value in display field 4: Compr. ON
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24-162

- Depress gas pedal completely (swiftly) and then
release it (brief acceleration).


Specified value in display field 4: Indication
jumps for a few seconds from "Compr. ON"
to "Compr. OFF" (compressor is switched off
when vehicle accelerates).
If indications do not resemble description:

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
A/C control
head -E87-
Terminal
41 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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24-170

Rapid data transfer
HELP
Select function XX

When indicated on display
Note:
Measuring value blocks 125 and 126 indicate the participants in the
powertrain data-BUS. - Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read measurin
g value block
Q
Enter displa
y group number XXX

When indicated on display
- Press buttons -1-, -2- and -5- to select "display group number 125" and
press -Q- button to confirm input.
Read Measuring Value Block 125
1
2
3
4

When indicated on display
- Check indications in display fields 1 through 4.
CAN capable control modules connected to the Engine Control Module
(ECM) are indicated:

No indication: Control module not CAN-capable
Indication 1: CAN capable control module is connected to databus
Indication 0: CAN capable control module is not connected to
databus
Read Measuring Value Block 126
1
2
3
4

- Check under display group 126 in the same manner.
-
Press button.
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24-171

Rapid data transfer
HELP
Select function XX

When indicated on display
- Press buttons -0- and -6- to select "End output" and press -Q- button to
confirm input.
Rapid data transfer
HELP
Enter address word XX

When indicated on display
When a control module responds with its identification, the display
indicates the number of stored errors or indicates "no malfunctions
recognized".
DTCs stored in the system are indicated in sequence and printed out.
Then the VAG1551 scan tool sends the next address word. - Press button 0- twice to select "Automatic test sequence", address
word 00. Press -Q- button to confirm input.

DTC memory of all OBD capable systems in the vehicle will be
checked.
VAG - On Board Dia
gnostic
(OBD
) HELP
1- Rapid data transfer*2- Blink code output*

The automatic test sequence is over when the following indication
appears on the display
If a malfunction related to the"powertrain databus" or the "CAN-bus" is
indicated:
- Check whether the Engine Control Module (ECM) and other CAN
capable control modules installed are appropriate for this vehicle (part
no. and coding).
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24-176

If you cannot determine a cause for the DTC
"Powertrain databus malfunction, check
whether the DTC is caused by one of the
control modules.
All control modules that use the CAN-bus are still
disconnected. Ignition is switched off.

- Connect one control module.

- Connect VAG 1551 scan tool. Switch ignition on,
and erase DTC memory of control module just
connected. End scan tool output using "End
Output" function 06.

- Switch ignition off and then on.

- Leave ignition on for 10 seconds. Read DTC
memory of control module just connected.

- If DTC "Powertrain databus malfunction" is
displayed, replace control module just
connected.

- If DTC "Powertrain databus malfunction" is not
displayed, connect next control module and
repeat procedure.
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