wiring AUDI A4 1996 B5 / 1.G APB Engine Additional Signals Checking Workshop Manual

24-179


Additional signals, checking

Engine speed (RPM) signal, checking


Note:
The engine speed signal is taken from terminal
37 on the Engine Control Module (ECM). The
signal is used for various functions including the
RPM display in the instrument cluster.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
- Check wiring from test box socket 37 to instrument cluster according to
wiring diagram for an open circuit.
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Fuel consumption signal for on-board
computer, checking


Notes:

The fuel consumption signal is calculated by the
engine control module (on the basis of the
injection period) and passed on to the on-board
computer. The fuel consumption signal is taken
from terminal 81 on the Engine Control Module
(ECM).
Checking fuel consumption signal

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
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24-181

Coolant temperature signal, checking


Notes:

The engine control module receives the coolant
temperature signal from the instrument cluster.
When the signal is received, the charge
pressure is reduced to prevent the engine from
overheating.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
- Check wiring from test box socket 19 to instrument cluster according to
wiring diagram for an open circuit.
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- Take vehicle for a test drive and check whether
vehicle speed appears in display field 3.

- If vehicle speed does not appear, raise the
vehicle (preferably using a lift) until front left
wheel is clear of the ground.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1598/31 test box to wiring harness for engine control
module. Do not connect to the engine control module itself Page 24
-
20
.
- Connect diode test lamp between socket 3 (B+) and socket 54 (vehicle
speed signal).
- Switch ignition on and turn front left wheel by hand.
The diode test lamp should flash (very brief flashes).
- If diode test lamp does not flash, check for open circuit or short to B+
or Ground (GND) in wiring between instrument panel and terminal 54
on engine control module connector.
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24-184

Fuel tank level signal, checking


Note:

The Engine Control Module (ECM) receives the
fuel tank level signal from the instrument
cluster.
The processed signal enters on terminal 30 the
Engine Control Module (ECM) and is used to
determine certain malfunctions (e.g.: misfire)

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.

- Check wiring from test box socket 30 to
instrument cluster according to wiring diagram
for an open circuit and short circuit to B+/Ground
(GND).
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24-189
If specifications are not met:

Check voltage supply

- Connect VAG1527 B between following sockets
on harness connector:

Harness connector
terminal
Measure
against
1 Ground (GND)


The LED must come on
Harness connector
terminal
Measure
against
3 Ground (GND)

- Switch ignition on.


The LED must come on
If LED does not come on:

- Check wiring connection from terminal 1 or 3 of
connector for open circuit (fuse) or short circuit
to Ground (GND).
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Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- If necessary eliminate open circuit or short
circuit to Ground (GND)
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If LED comes on:

Check activation

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.
Test the following wiring connections for open
circuits and short to B+ or Ground (GND):

Harness
connector
terminal
VAG1598/31 test box,
socket
2 56
4 55

- Repair any open/short circuit as necessary.
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24-194
If specification is obtained:

Check voltage supply

- Connect VAG1527 B between following sockets
on harness connector:

Harness connector
terminal
Measure
against
2 Ground (GND)

- Switch ignition on.


The LED must come on
If LED does not come on:

- Check wire connection from terminal 2 of
connector for open circuit (fuse) or short circuit
to Ground (GND).

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

- If necessary eliminate open circuit or short
circuit to Ground (GND)
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24-195
If LED comes on:

Check activation

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.
Test the following wiring connections for open
circuits and short to B+ or Ground (GND):

Harness
connector
terminal
VAG1598/31 test box,
socket
1 39

- Repair any open/short circuit as necessary.
Pa
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pair&id=AUDI.B5.FU04.24.6