sensor AUDI A4 1999 B5 / 1.G ATW Engine Ignition System Workshop Manual

28-21


Intake Air Temperature (IAT) sensor -G42-,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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28-22
Component location Overview of component
locations Page 24
-5

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 display group number XXX

When indicated on display
- Press buttons -0-, -0- and -4- to select "display group number 004" and
press -Q- button to confirm input.
Read Measuring Value Block 4
1
2
3
4

Indicated on display
- Check specified value for Intake Air Temperature (IAT) sensor in
display field 4:
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28-23


Display fields

1 2 3 4
Display group 004: Intake Air Temperature (IAT), engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant
temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C
Specified value xxxx/min 12.0 to 15.0 V
80.0 to 110.0 C
From ambient temperature up to 110
C
1)
1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor and sensor wires for
contact resistances and open circuit.
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28-24

Checking wire connections

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

- Disconnect connector -1- at Intake Air Temperature (IAT) sensor -G42-
(item no. 2).

- Check following wire connections for open circuit and short circuit to
Ground (GND) and B+: Harness connector
Terminal
VAG1598/31 test box
Socket
1 85
2 108
- Check both wires to each other for short circuit.
- Repair open circuit or short circuit if necessary.
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28-25
If no malfunctions are found in wires:

Check sensor:

Specified values
If specified value is not obtained: - Connect multimeter at sensor for resistance measurement.Temperature C
Resistance k
-20 approx. 13.8
0 approx. 5.5
20 approx. 2.4
40 approx. 1.1
60 approx. 0.6
- Replace Intake Air Temperature (IAT) sensor.
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28-26


Engine speed (RPM) sensor -G28-,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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28-27
Component location Overview of component
locations Page 24
-5

Note:
The engine speed (RPM) sensor detects RPM
and reference marks. The engine cannot be
started without a signal from the engine speed
(RPM) sensor -G28-. If the engine speed (RPM)
sensor -G28- signal fails while the engine is
running, the engine will stop immediately.

Test sequence

- Before performing test, check sensor for proper
installation and proper fitting.

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect harness connector for engine speed (RPM) sensor -G28-
(item no. 3) in engine compartment.
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28-28


Note:
Resistance value of the engine speed (RPM) sensor is based on a
temperature of 20 C. Resistance increases as temperature increases.
If specified value is not obtained:
If specified value is obtained: - Connect multimeter between terminal 1 and 2 for resistance
measurement.

Specification: 730 to 1000
- Replace engine speed (RPM) sensor.

If specified value is not obtained: - Connect multimeter to terminals 1 and 3 (shielding) and to terminals 2
and 3 (shielding) for resistance measurement.

Specification: each (no continuity)
- Replace engine speed (RPM) sensor.
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28-30


Engine Coolant Temperature (ECT) sensor
-G62-, checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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28-32


Display fields

1 2 3 4
Display group 004: Coolant temperature, engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C

Specified value xxxx/min 12.0 to 15.0
V Temperature value must rise
evenly From ambient temperature up to
110 C
If display field 3 does not have a realistic
indication:

- Disconnect connector at coolant temperature
sensor.

Coolant temperature sensor with square
connector:

- Connect multimeter between terminal 1 and 3 of sensor for resistance
measurement.
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