1995 AUDI A4 ATQ Engine Ignition System Checking Workshop Manual

28-14


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

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3B
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28-15
Component location Overview of Component
Locations, page Page 24
-5

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Ignition must remain switched on for this.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
Input 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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28-16


Display fields

1 2 3 4
Display group 004: Intake Air Temperature (IAT), engine at idle
Display xxxx/min xx.xxx volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery voltage Coolant
temperature Intake Air Temperature (IAT)
Functional
range 630 to 6800 RPM 10.000 to 15.000
V -48.0 to 143.0 C
-48.0 to 143.0 C
Specified value xxxx/min 12.000 to 15.000
V 80.0 to 110.0 C
From ambient temperature up to 120
C
1)
1) Approximate values: While driving, up to 24 C above ambient temperature. If heated while standing, up to 120 C is
possible.
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28-17

Checking wire connections

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the 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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28-18
If no malfunctions are found in wire:

Check sensor:

- Disconnect connector from Intake Air
Temperature (IAT) sensor.

Specified values
Example:
If air temperature is in a range from 0 C to 20 C, the resistance value
must be between 5 k and 2.4 k
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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28-19


Engine speed (RPM) sensor -G28-,
checking

Special Tools and Equipment

VAG1526A
VAG1594A
VAG1598/31
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28-20
Component location Overview of Component
Locations, page 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.

- Disconnect harness connector for the engine
speed (RPM) sensor (identification: gray
harness connector).

Note:
Resistance value of the engine speed (RPM) sensor is based on a
temperature of 20 C. Resistance increases as temperature increases. - Connect multimeter between terminal 2 and 3 for resistance
measurement.

Specification: 730 to 1000
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28-21
If specified value is not obtained:

- Replace engine speed (RPM) sensor.
If specified value is obtained:

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

Specification: each (no continuity)
- Replace engine speed (RPM) sensor.
- Connect VAG1598/31 test box at wiring harness to ECM, do not
connect ECM Page 24
-17
.
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