AUDI A3 1995 8L / 1.G ATW Engine Additional Signals Workshop Manual

24-155


Additional signals, checking Special tools and equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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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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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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- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Connect VAG1527B voltage tester to sockets 3
(B+) and 54 (VSS) of VAG1598/31 test box.

- Switch ignition on and turn front left wheel by
hand.


LED must blink (very brief blink signal).
If LED does not blink:

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

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
54 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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24-160

A/C compressor shut-off, checking


Note:

The A/C compressor signal communicates to
the ECM that the compressor will be switched
on in 140 ms.
The Engine Control Module (ECM) can switch
off the A/C compressor via the same wire
connection.
Engine Control Module (ECM) switches off A/C
compressor:

-- during hard acceleration (Wide Open
Throttle 1st gear)

-- in emergency mode (emergency
operation)

-- after initiating basic setting (function 04)

Test requirements:
A/C system OK
No DTCs in DTC memory of Engine Control
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Module (ECM).
Vehicle at room temperature (warmer than
+15 C).
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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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- 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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- If there are no malfunctions in the wiring, check
function of A/C system.

Repair Manual, Heating & Air Conditioning,
Repair Group 01; On Board Diagnostic (OBD) of A/C system

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