AUDI A4 1995 B5 / 1.G APB Engine Ignition System Checking

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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28-20
If no malfunction in wire is detected:

Checking sender

- Measure resistance between contacts 1 (signal) and 2 (Ground GND))
on connector for Intake Air Temperature (IAT) sensor -G42. Temperature C
Resistance k
-20 approx. 13.8
0 approx. 5.5
20 approx. 2.4
40 approx. 1.1
60 approx. 0.6
- If value does not match the specification, replace intake air
temperature sensor.
- In order to install a new sensor, the intake manifold must first be
removed Page 24
-15
.
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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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follows:
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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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28-25

Engine Coolant Temperature (ECT)
sensor -G62, checking


Note:
Component location of coolant temperature
sensor Page 24
-5 .

Test conditions

Engine cold

- Connect vehicle diagnostic, testing and
information system VAS 5051 or VAG1551 scan
tool to vehicle and select engine electronics
control module by entering address word "01"
Page 01
-9 .

When doing this the engine must be at idle.
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28-26

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 Measuring Value Block 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
- Check readout for coolant temperature sender in display field 3.
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28-27


Display fields

1 2 3 4
Display Group 004: Coolant temperature with engine idle
Display xxxx RPM xx.xxx V
xxx.x C
xxx.x C
Indicates Engine speed RPM Battery voltage
Coolant temperature Intake air temperature
Specified value XXXX RPM 12.000...14.500 V
Temperature must increase evenly Ambient temperature
until 120 C
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