1996 AUDI A4 engine

28-13
If the specifications are not obtained:

- Switch ignition off.

- Connect test box VAG 1598/31 to wiring
harness for engine control module. Do not
connect to the engine control module itself.
Page 24
-20
.

The following wiring connections are to be checked for open circuits
and/or short to B+ or Ground (GND).
Black 4-pin connector on wiring
harness, terminal VAG1598/31 test box,
socket
1 94
3 110
4 102 Brown 4-pin connector on wiring
harness, terminal VAG1598/31 test box,
socket
1 95
3 111
4 103
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28-17

Intake Air Temperature (IAT) sensor -
G42, checking

Location of sensor and connector Page 24
-5 .

- Connect vehicle diagnostic, testing and
information system VAS 5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page
01
-9 . When doing this the ignition must be
switched on.
Rapid data transfer
HELP
Select Function XX

Indicated on display
- Press buttons -0- and -8- to select function "Read Measuring Value
Block" and confirm entry with -Q- button.
Read Measurin
g Value Block
HELP
Input Displa
y Group Number XXX

Indicated on display
- Press buttons -0-, -0- and -4- to select Display Group 4 and confirm
entry with -Q- button.
Read Measuring Value Block 4
1
2
3
4

Indicated on display: (1...4 display fields) - Check display value for intake air temperature sensor (display field 4):
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28-18


Display fields

1 2 3 4
Display Group 004: Intake air temperature with engine idling
Display xxxx rpm xx.xxx V
xxx.x C
xxx.x C
Indicates Engine speed Battery voltage Coolant temperature
Intake air temperature
Work range min.: 750 RPM
max.: 6800 RPM min.:10.000 V
max.: 15.000 V min.: -48.0 C
max.: 143.0 C
min.: -48.0 C
max.: 143.0 C
Specified value xxxx RPM 12.000...15.000 V
80.0...110.0 C
Between ambient temp. and 120 C
1)
1) If there is a large difference between the temperature displayed and the ambient temperature at the sensor, check the
sensor and sensor wiring for contact resistance and open circuit.
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28-19

Checking wiring:

- Switch ignition off.

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

- Check for open circuit in wiring between test box and 2 pin harness
connector using wiring diagram.

Specified value: max. 1.5
Terminal on 2-pin harness
connector
Contact on control module
connector or test box
1
2 85
108
- Check wiring for short circuits to each other between contacts 1 and 2
on 2-pin connector. Also test for short circuits to B+ or Ground (GND).
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28-21

Engine Speed (RPM) sensor -G28,
checking


Note:

The engine speed sender is a combined speed
sender and reference mark sender. Without a
signal from the Engine Speed (RPM) sensor -
G28 the engine cannot be started. If the signal
from the Engine Speed (RPM) sensor -G28 fails
while the engine is running, the engine will cut
out immediately.

Checking Engine Speed (RPM) sensor
Component location of sensor and connector
Page 24
-5 .

- Before carrying out test, make sure that sensor
is correctly installed and firmly seated.

- Disconnect harness connector for Engine Speed
(RPM) sensor (grey connector).
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28-22


Notes:
If the specification is not attained:
If the specification is attained:
If the specification is not attained:
If the specification is attained: - Connect multimeter (Fluke 83 or equivalent) (resistance test range) to
terminals 2 and 3 on connector for engine speed sensor using test lead
from VAG1594 connector test kit.
Specified value: approx. 730 - 1000 ohm
The resistance value for the engine speed sensor is based on a
temperature of 20 C. The resistance increases as the temperature rises.
- Replace engine speed sensor.
- Connect multimeter (Fluke 83 or equivalent) (resistance test range)
between terminals 2 and 1 (Ground (GND)) and between terminals 3
and 1 (Ground (GND)).

Specified value: R (infinite Ohms / open circuit) in each test
- Replace Engine Speed (RPM) sensor.
-
Check wiring between sensor connector and engine control module as
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28-23

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

Specified value: max. 1 .
Specified value: max. 1 .
Specified value: max. 1 . - Test continuity of screening (shielded wire) between contact 1 on
engine speed sender connector and socket 108 on test box. - Test continuity of negative wire from contact 2 on sender connector to
socket 90 on test box. - Test continuity of signal wire from contact 3 on sender connector to
socket 82 on test box.
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28-24
If the values are not as specified:

- Rectify short or open circuit in wiring between
sender connector and control module connector.

Terminal on sensor
connector
Terminal on control
module connector
1
2
3 108
90
82

- If no open circuits or short circuits are identified,
replace Engine Control Module (ECM) Page
24
-24
.
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